Packed with caramelized onions, creamy brie, and fragrant thyme, all baked in a flaky puff pastry, this upside down onion tart is a show-stopping dish that’s sure to impress.
Upside down tarts are having their *moment*, and I am here for it. From fruity to savory, the concept is simple – assemble the tart upside down, bake, then flip.
This tasty twist on a classic tart involves creating a caramelized and cheesy masterpiece by assembling the ingredients upside down and flipping it over after baking. With layers of puff pastry, balsamic-glazed onions, fragrant thyme, and creamy brie cheese, these tarts are not only visually stunning but also a delicious delight.
Here’s What You’ll Need
- Puff Pastry: The flaky and buttery puff pastry serves as the base for our tart, providing a light and crisp texture that complements the caramelized onions and brie cheese.
- Olive Oil: The drizzle of olive oil adds a rich and savory flavor to the tart, while also helping everything to not stick to the parchment.
- Balsamic Glaze: The sweet and tangy balsamic glaze adds depth and complexity to the tart, balancing the flavors of the onions and cheese while giving a delightful hint of acidity. I like using glaze (instead of vinegar), which is thicker and sweeter.
- Thyme: The aromatic thyme leaves bring an earthy note to the tart. You could also use rosemary here!
- Salt and Pepper: These common seasonings enhance the flavors of all the ingredients, providing a balanced and well-seasoned tart.
- Onions: The thinly sliced onions become wonderfully caramelized during baking, adding a sweet and savory element to the tart.
- Brie: The creamy and indulgent brie cheese melts beautifully, creating a luscious and gooey layer that pairs perfectly with the sweet caramelized onions.
- Egg: The beaten egg is used to brush the pastry, giving it a beautiful golden color and a glossy finish after baking.
Puff pastry can usually be found in the frozen section of most grocery stores, and balsamic glaze can be found in the condiment aisle or specialty food stores.
How to make Upside Down Onion Tarts
Despite looking fancy and complicated, these upside down onion tarts are remarkable simple to make.
Step 1: Prep
If using frozen puff pastry, allow it to thaw at room temperature until soft and pliable. This step is important to ensure that the pastry is easy to work with and will bake evenly. Once thawed, cut the puff pastry into 8 equal squares, which will serve as the individual bases for the upside-down onion tarts. Preheat the oven to 400°F (204°C) now so it’s ready to go when you are!
Step 2: Layer
Line a large baking sheet with parchment paper to prevent the tart from sticking and make clean-up easier. Drizzle equal amounts of olive oil on the parchment-lined baking sheet, creating small puddles. Drizzle balsamic glaze over the olive oil. Placing an onion slice on each puddle creates a base for the tart and allows the onions to cook and caramelize beautifully. Sprinkle with thyme, salt, and pepper, and top with brie triangles for a flavorful and melty tart!
Step 3: Cover
Cover the onion slices with the puff pastry squares, ensuring that the cheese and onions are completely covered. This will create a golden and flaky crust that encases the caramelized onions and creamy brie.
Brushing the pastry with whisked egg will give it a beautiful shine and help it bake to a perfect golden brown.
Step 4: Bake
Bake the tart until golden brown and cooked through. Cool briefly before removing from parchment (if you find the onion sticking to the parchment, let it cool more before enjoying).
- Change Up The Onions: Experiment with different types of onions to vary the flavor profile. Sweet onions like Vidalia or red onions work well in this recipe, but you can also try using shallots or leeks for a unique twist.
- Different Cheese: If you prefer a stronger cheese flavor, you can use a different type of cheese instead of brie. Goat cheese or blue cheese can add a tangy and distinct taste to the tart.
- Optional Add-Ins: To enhance the flavor, consider adding additional ingredients such as sliced mushrooms, roasted garlic, or even a drizzle of honey.
To store the onion tarts, allow them to cool completely at room temperature. Once cooled, place them in an airtight container or wrap them tightly with plastic wrap. They can be stored in the refrigerator for up to 2-3 days.
To reheat the tarts, pop them in the oven or air fryer to restore their crispness and warm them up. (It’s best to consume the tarts fresh for the optimal texture and flavor. Reheating may result in a slightly softer crust, but the caramelized onions and melted cheese will still be delicious.)
This large nonstick sheet pan is one of my everyday favorites!
- 1 17.3 oz package puff pastry 2 sheets, 490 g
- 4 Tbsp olive oil 60 mL
- 4 Tbsp balsamic glaze 60 mL
- 8 sprigs fresh thyme
- 8 pinches salt and pepper
- 2 medium onions peeled and thinly sliced
- 1 wheel brie cheese cut into 8 triangles
- 1 large egg
- Prep: If frozen, let pastry thaw on the counter until soft and pliable. Once thawed, cut into 8 equal squares. Preheat oven to 400°F (204°C). Slice the onion and remove thyme leaves from stems.
- Layer: Line a large baking sheet with parchment paper. Drizzle oil equally around the baking sheet to make 8 little puddles. Drizzle on balsamic. Top each with an onion slice. Sprinkle on thyme leaves, salt, and pepper. Top with a slice of brie.
- Cover: Top each mound with the puff pastry, pressing the edges down to completely cover the cheese and onion. Whisk the egg together then brush it over the pastry.
- Bake: Bake on the middle rack for 15 minutes, or until golden brown and cooked through. Let cool on the baking sheet for a few minutes before trying to remove from the parchment.