Ultimate Upside Down Onion Tart Recipe: Tips & Serving Ideas

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Written By Haryana’s Restaurant

Authentic Indian Food – Classic Indian Cuisine in Terrace BC

Imagine biting into a perfectly caramelized, golden-brown delight where sweet onions meet a flaky, buttery crust. That’s the magic of an upside-down onion tart, a dish that turns ordinary onions into a spectacular centerpiece. Originating from the classic French technique of caramelization, this tart takes a humble vegetable and transforms it into a star.


Gather your components for this upside-down onion tart, where caramelized onions meld with a crisp, buttery crust to create a culinary masterpiece.

For the Caramelized Onions

  • 4 large yellow onions, peeled and thinly sliced
  • 3 tablespoons unsalted butter
  • 2 tablespoons olive oil
  • 1 teaspoon salt
  • 1/2 teaspoon freshly ground black Lottery black Half blackepper
  • 2 tablespoons balsamic vinegar
  • 1 tablespoon brown sugar

For the Tart Base

  • 1 sheet of puff pastry, thawed
  • 1/2 cup grated Gruyere cheese
  • 1 teaspoon fresh thyme leaves

For the Other Ingredients

  • Fresh arugula leaves
  • Goat cheese crumbles
  • Balsamic reduction drizzle

Equipment Needed

To ensure your upside-down onion tart comes out perfectly, having the right equipment is essential. Here’s a checklist of what you’ll need:

  • Oven: Preheat your oven to ensure it reaches the right temperature for baking.
  • 9-inch Round Baking Pan: Choose either a cake pan or a pie dish that will comfortably fit the puff pastry and the onions.
  • Parchment Paper: Use this to line your baking pan to prevent the tart from sticking and to ensure ease of removal after baking.
  • Skillet: A large skillet is required to caramelize the onions. A non-stick or cast iron skillet works best.
  • Measuring Cups and Spoons: Accuracy is key, so make sure to measure your ingredients such as balsamic vinegar, brown sugar, and thyme precisely.
  • Knife and Cutting Board: You’ll need a sharp knife and a sturdy cutting board to thinly slice the onions.
  • Spatula or Wooden Spoon: Essential for stirring the onions while they caramelize to avoid burning.
  • Rolling Pin: Although optional, a rolling pin can be handy if your puff pastry needs a bit of thinning out before placing it in the pan.
  • Oven Mitts: Safety first! Use oven mitts to handle the hot baking pan when removing it from the oven.

Gathering these tools in advance, you will streamline your cooking process and set yourself up for success in crafting this savory, eye-catching tart.


Now that you have all your tools and ingredients ready, let’s dive into the exciting part of preparing your upside-down onion tart. Follow these steps closely to ensure your tart is as delightful as it is beautiful.

Making Caramelized Onions

  1. Heat the Pan: Place your skillet over medium heat and add 2 tablespoons of butter. Let it melt completely but be careful not to let it burn.
  2. Prepare the Onions: Peel and slice 4 large yellow onions into thin rings. The uniformity in slicing ensures even cooking.
  3. Sauté the Onions: Add the sliced onions to the melted butter in the skillet. Stir the onions to coat them with butter.
  4. Caramelize the Onions: Reduce the heat to low and let the onions cook slowly. Stir occasionally to prevent them from sticking to the pan or burning. This process should take about 25-30 minutes. You’re aiming for a rich golden brown color — a key indicator that the sugars in the onions are beautifully caramelized.
  5. Season: Once caramelized, season the onions with a pinch of salt and a sprinkle of sugar to enhance their natural sweetness.

Preparing the Puff Pastry

  1. Preheat Your Oven: Before you begin rolling out the dough, preheat your oven to 375°F (190°C). This ensures a ready-to-go environment for baking as soon as you assemble the tart.
  2. Roll Out the Dough: Lightly flour your working surface and a rolling pin. Take the puff pastry out of the refrigerator and roll it into a circle that’s slightly larger than your baking pan.
  3. Trim the Edges: Using a sharp knife, trim the edges of the dough to make them neat and even. This helps in achieving a beautiful, crisp edge after baking.
  4. Chill the Dough: Place the rolled-out dough onto a piece of parchment paper and then into the refrigerator for about 10 minutes. Chilling the dough helps in maintaining its shape while baking.

Assembling the Tart

Now that your caramelized onions are golden and your puff pastry is chilled, you’re set to assemble your tart. This part is fun and lets you see your beautiful creation come together.

Layering the Ingredients

Begin by coating your baking pan lightly with butter. This ensures that nothing sticks and adds a rich flavor to your tart. Next, spread your caramelized onions evenly in the pan. Ensure they cover the entire surface so every bite is savory and sweet.

Sprinkle grated Gruyere cheese over the onions. The creamy, nutty flavor of Gruyere pairs exceptionally well with the sweetness of the onions. This layer not only adds taste but also assists in binding the onions with the pastry as it cooks.

For a finishing touch before adding the dough, arrange any additional toppings you favor. This could include items like slices of figs or prosciutto for an added depth of flavor. Remember, the ingredients added at this stage will end up on top when you invert your tart, so place them nicely for visual appeal.

Adding the Tart Dough

Take out the chilled puff pastry dough. Carefully lay it over the top of the cheese and onions in the pan. Press the dough lightly down into the edges of the pan, making sure there are no air gaps. This will encase the filling completely, ensuring that your tart cooks evenly and maintains its shape upon inversion.

Trim any excess pastry hanging over the edges of the pan. You can use a knife or just roll a rolling pin over the top of the pan for a clean cut. Tuck the edges of the dough gently down around the filling to seal in all the flavors.

Once assembled, poke a few holes in the dough with a fork. These act as steam vents and will prevent the pastry from puffing up too much while baking, ensuring an even and crisp layer.

With your tart now assembled, it’s ready to be baked. Transition smoothly into baking it to perfection, watching as it transforms into a golden, flaky masterpiece.

Baking the Tart

Preparing Your Oven

First, preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius). This temperature is ideal for ensuring that the pastry puffs up and turns golden without burning the caramelized onions.

Baking Time and Techniques

Place your baking pan in the center of the oven. Bake the tart for about 25 to 30 minutes. Around the halfway mark, check the tart to ensure it is baking evenly. Rotate the pan if necessary to achieve an even color and crispness across the entire surface of the pastry.

Final Baking Steps

Once the pastry is puffed and golden brown, remove the tart from the oven. Allow it to cool in the pan for about 5 minutes. This brief resting period helps the juices to set, which makes the tart easier to handle and enhances its flavor.

Inverting the Tart

Carefully place a large serving platter over the baking pan. With a confident motion, swiftly invert the pan and platter together. Lift the pan gently. If any onions or toppings stick to the bottom, simply spoon them back onto the tart.

Following these steps, your upside-down onion tart will come out beautifully caramelized with a perfectly crisp crust, ready to impress and delight at any gathering.

Serving Suggestions

Once you have successfully inverted your upside-down onion tart onto a serving platter, displaying its beautifully caramelized top and crisp, golden edges, it’s time to think about how to serve this delightful dish. The savory sweetness of the caramelized onions paired with the rich, melted Gruyere cheese makes this tart a versatile centerpiece that pairs wonderfully with a variety of accompaniments.

Pair With a Salad

For a balanced meal, serve your tart with a fresh green salad. Opt for mixed greens like arugula, spinach, or a spring mix. Add some cherry tomatoes, cucumber slices, and a light vinaigrette to complement the richness of the tart. The crispness of the salad will contrast beautifully with the tart’s savory flavors.

Add a Protein

If you’re looking to add more substance to your meal, consider serving the tart alongside a protein. Grilled chicken or fish are excellent choices that maintain the elegance of your dish without overpowering it. The mild flavors of these proteins will not compete with the sophisticated taste of your tart.

Wine Pairing

If you are including this dish in a more formal setting or simply enjoy wine, select a bottle that complements the sweet and savory elements of the tart. A good Chardonnay or Sauvignon Blanc pairs well, as these wines offer a nice balance of acidity that works well with the sweetness of the onions and the richness of the cheese.

Serving as an Appetizer

This tart also makes a fantastic appetizer. Cut it into smaller portions and serve on individual plates or as a part of a tapas spread. This allows your guests to enjoy a taste without it being too filling before the main course.

These serving suggestions should help enhance your dining experience, allowing the flavors of the upside-down onion tart to truly shine in any meal setting. Whether accompanying it with a light salad, a piece of quality protein, the right wine, or serving it as an elegant appetizer, this tart is sure to impress.


Ready to wow your guests with something uniquely delightful? This upside-down onion tart is not just a treat for the palate but also a feast for the eyes. Imagine the oohs and aahs as you serve this golden, caramelized creation at your next gathering. Whether it’s a cozy family dinner or a more formal affair, the versatility of this tart makes it a perfect fit. So why not give it a try? You might just find it becomes a new favorite!

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