Upside Down Onion Tart – Easy Caramelized Delight

I still remember the first time I tried an upside-down tart in a tiny bistro in Paris. The waiter set it down with a flourish, and when I flipped it onto my plate, the caramelized onions glistened like jewels. I knew I had to recreate that magic at home – minus the beret and the jet lag.

This Upside Down Onion Tart is my weeknight shortcut to that Parisian memory. It uses store-bought puff pastry, so you get all the flaky, buttery goodness without the fuss. The onions slowly caramelize into sweet, jammy perfection, and the goat cheese adds a tangy twist that makes every bite irresistible.

Whether you're serving it as an appetizer, a light lunch with a green salad, or a stunning side dish, this tart is guaranteed to impress. And the best part? It's surprisingly simple to make. So grab your onions and let's get flipping!

About the Ingredients

2 tablespoons (28g) unsalted butter, plus extra for greasing

Use unsalted to control salt. You can substitute olive oil for a dairy-free version.

3 large (about 600g) yellow onions, thinly sliced

Yellow onions caramelize beautifully. Sweet onions like Vidalia also work well.

1 teaspoon (5g) granulated sugar

Helps speed up caramelization. You can omit if using very sweet onions.

1/2 teaspoon (2g) salt

Kosher salt preferred. Adjust to taste.

1/4 teaspoon (0.5g) black pepper, freshly ground

Adds a subtle kick. You can use white pepper for a milder flavor.

1 tablespoon (15ml) balsamic vinegar

Adds depth and tang. Red wine vinegar or sherry vinegar are good substitutes.

1 sheet (about 250g) puff pastry, thawed

Use all-butter puff pastry for best flavor. If frozen, thaw overnight in the fridge.

4 oz (115g) goat cheese, crumbled

Tangy and creamy. Feta or blue cheese can be substituted.

1 teaspoon (1g) fresh thyme leaves, plus more for garnish

Adds an earthy note. Dried thyme works in a pinch (use 1/2 teaspoon).

Tips & Tricks

Don't rush the onions

Caramelizing takes about 20-25 minutes. Low and slow is key to avoid burning.

Keep the pastry cold

Work quickly and return it to the fridge if it gets too warm. Cold pastry puffs up better.

Grease your pan well

Use a nonstick tart pan or a cake pan lined with parchment for easy flipping.

Step-by-Step Instructions

1. Preheat and Prep Pan

Preheat your oven to 400°F (200°C). Grease a 9-inch (23cm) round tart pan or cake pan with butter. Set aside.

2. Caramelize the Onions

In a large skillet, melt the butter over medium heat. Add the sliced onions, sugar, salt, and pepper. Cook, stirring occasionally, for 20-25 minutes until the onions are deep golden brown and jammy. Stir in the balsamic vinegar and cook for 1 more minute. Remove from heat.

3. Layer the Onions

Spread the caramelized onions evenly over the bottom of the prepared pan. Sprinkle the crumbled goat cheese and thyme leaves over the onions.

4. Top with Pastry

Roll out the puff pastry slightly on a floured surface to about 10 inches (25cm) round. Drape it over the onions, tucking the edges down the sides of the pan. Prick the pastry with a fork to allow steam to escape.

5. Bake Until Golden

Bake for 25-30 minutes until the pastry is puffed and deep golden brown. If the top browns too quickly, tent loosely with foil. The tart is done when the pastry is crispy and the edges are bubbling.

6. Cool and Flip

Let the tart cool in the pan for 5 minutes. Place a serving plate over the pan and carefully invert the tart onto the plate. Lift off the pan.

7. Garnish and Serve

Sprinkle with fresh thyme leaves. Slice and serve warm or at room temperature.

Delicious Variations

Add sliced mushrooms

Sauté with the onions for an earthy twist.

Swap the cheese

Use blue cheese or sharp cheddar instead of goat cheese.

Make it herby

Add chopped rosemary or sage along with the thyme.

How to Store Upside Down Onion Tart

Frequently Asked Questions

I hope you enjoy this upside-down onion tart as much as I do. It's a little slice of Paris you can make any night of the week. Happy cooking, and remember – you're doing better than you think.

Upside Down Onion Tart

Upside Down Onion Tart with buttery puff pastry, sweet caramelized onions, and tangy goat cheese – an elegant yet easy savory tart.

★★★★½ 4.8 (156 ratings)

15 minPrep time35 minCook time6Servings285 kcalCalories

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🧂 Ingredients

• 2 tablespoons (28g) unsalted butter, plus extra for greasing
• 3 large (about 600g) yellow onions, thinly sliced
• 1 teaspoon (5g) granulated sugar
• 1/2 teaspoon (2g) salt
• 1/4 teaspoon (0.5g) black pepper, freshly ground
• 1 tablespoon (15ml) balsamic vinegar
• 1 sheet (about 250g) puff pastry, thawed
• 4 oz (115g) goat cheese, crumbled
• 1 teaspoon (1g) fresh thyme leaves, plus more for garnish

📋 Instructions

1. 1Preheat and Prep Pan — Preheat your oven to 400°F (200°C). Grease a 9-inch (23cm) round tart pan or cake pan with butter. Set aside.
2. 2Caramelize the Onions — In a large skillet, melt the butter over medium heat. Add the sliced onions, sugar, salt, and pepper. Cook, stirring occasionally, for 20-25 minutes until the onions are deep golden brown and jammy. Stir in the balsamic vinegar and cook for 1 more minute. Remove from heat.
3. 3Layer the Onions — Spread the caramelized onions evenly over the bottom of the prepared pan. Sprinkle the crumbled goat cheese and thyme leaves over the onions.
4. 4Top with Pastry — Roll out the puff pastry slightly on a floured surface to about 10 inches (25cm) round. Drape it over the onions, tucking the edges down the sides of the pan. Prick the pastry with a fork to allow steam to escape.
5. 5Bake Until Golden — Bake for 25-30 minutes until the pastry is puffed and deep golden brown. If the top browns too quickly, tent loosely with foil. The tart is done when the pastry is crispy and the edges are bubbling.
6. 6Cool and Flip — Let the tart cool in the pan for 5 minutes. Place a serving plate over the pan and carefully invert the tart onto the plate. Lift off the pan.
7. 7Garnish and Serve — Sprinkle with fresh thyme leaves. Slice and serve warm or at room temperature.

👨‍🍳 Chef's Note: For a vegan version, use dairy-free butter and omit the goat cheese or use a plant-based alternative.

Servings: 6

Cuisine: French-inspired

Course: Savory Tart

Nutrition (per serving): 285 kcal · 7g protein · 24g carbs · 18g fat

Written by Sofia Ramirez
Sofia writes about parenting and family wellness, exploring the messy, joyful reality of raising kids. She offers relatable stories and practical advice on everything from sleep training to managing screen time, always with a dose of humor.