These upside down puff pastry tarts are one of those dangerously simple recipes that feel far more impressive than the effort required. Crisp, flaky pastry. Jammy caramelised red onions. A hit of balsamic and fresh thyme. They bake, you flip, and suddenly everyone thinks you're a genius. Trust me, these disappear fast.
Upside down puff pastry tarts are especially popular during autumn and winter when onions are at their sweetest, but they shine year round as an easy starter, canapé, or light lunch. They are perfect for holidays like Christmas and Easter when oven space is tight and stress levels are high.
This recipe was inspired by another my upside down leek tart , and in fact this can be made with leeks too! The balance of flaky pastry and caramelised topping makes it incredibly versatile for entertaining.
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Ingredients
These ingredients were chosen because they do a lot of work with very little effort.
- Red onion: Sweet and mellow once baked.
- Puff pastry: Buttery and flaky, who wouldn't like it?
- Olive oil: Helps the onions caramelise and prevents sticking.
- Balsamic glaze: Thick, tangy, and perfect for creating a sticky glaze on the onion.
- Fresh thyme: Adds an earthy, aromatic note that lifts the dish.
See recipe card for quantities..
Instructions
Preheat the oven to 180C/350F(fan).
Prepare the pastry
Cut the puff pastry into even squares (8) and keep chilled while you prep the tray
Build the flavour base
Line a baking tray with parchment. For each tart, where the square is going to be, add ½ teaspoon olive oil, a drizzle of balsamic glaze, a pinch of salt, and a small sprig of thyme directly onto the paper. They might not off fit on one tray, you can separate them.
Add the onions
Place red onion slices on top, slightly overlapping, or use one large thicker slice if your onions are big.
Cover with pastry
Lay the puff pastry square over the onions. Press gently, seal the edges with a fork, and cut two shallow slits on top to control puffing.
Bake
Bake in the oven at 180C/350F(fan) until golden and fully puffed for 20-25 minutes.
Flip and serve
Flip with a spatufla while hot so the onions release cleanly and stay glossy.
Substitutions
Onion: Shallots can be used for a milder, sweeter result. Leeks can be used too.
Herbs: Rosemary or sage work well instead of thyme.
Gluten free: Use a gluten free puff pastry if available.
Storage
These tarts are best eaten fresh, but leftovers can be stored in an airtight container in the fridge for up to 2 days. Reheat in the oven to restore crispness.
FAQ
Can I use balsamic vinegar instead of glaze?
Yes, but reduce it first so it thickens, otherwise it may make the onions watery.
Do these work as canapés?
Absolutely. Cut smaller pastry squares and use thinner onion slices.
Is puff pastry vegan?
Most of the time yes, it's usually made with oil (instead of butter) as it's cheaper to produce. But do check the ingredients to make sure!
Related
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Did you make this recipe?
I love to see recreations and share them!
Upside Down Puff Pastry Tarts - With Onion
Ingredients
- 1 sheet puff pastry rectangular
- 5 small red onions sliced into ½ cm rounds
- 1½ tablespoons olive oil , divided
- 1½ tablespoons balsamic glaze divided
- 9 fresh thyme sprigs
- salt to taste
Instructions
- Preheat the oven to 180°C / 350°F fan assisted and line a baking tray with parchment paper.
- Cut the puff pastry sheet into 8 even squares.
- For each tart, add ½ teaspoon olive oil to the parchment, followed by ½ teaspoon balsamic glaze, a pinch of salt, and a small sprig of thyme.
- Arrange red onion slices on top, slightly overlapping, using about 2 to 3 slices per tart. If using bigger onions, use only 2 or 1 thicker one.
- Cover each onion stack with puff pastry. Press gently, seal the edges with a fork, and cut two shallow slits on top.
- Bake for 20-25 minutes, until deeply golden and fully puffed.
- Flip immediately while hot and serve.
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