These TikTok inspired upside down onion tarts, with their irresistible crunch and savory flavors, are the perfect party snack.
They’re buttery, crispy, flaky and have the deliciousness of caramelized onion and Gruyere cheese packed in a teeny, bite sized format that makes them perfect for your house parties!
The golden brown crispiness and the sweet and savory caramelized onion, teamed up with the cheese makes these an irresistible snack that everyone will love.
This quick and easy to make appetizer truly has my heart!
- What's So Great About the Recipe?
- Ingredients For the Upside Down Onion Tarts Recipe
- How to Make Upside Down Onion Tarts
- Substitutions & Variations
- 💭Top Tip
- How to Store Leftover Onion Tarts
- Tips & Tricks to Nail the Recipe
- How to Serve Upside Down Onion Tarts
- Related Recipes
- Upside Down Onion Tarts
- Food Safety
What's So Great About the Recipe?
My favorite part about these caramelized onion upside down tarts is the fact that they’re super easy to make.
You can actually put them together super quick, and get them ready to serve in under 30 minutes.
Plus, you can experiment with the fillings that go into it too- the recipe is adaptable that way!
Ingredients For the Upside Down Onion Tarts Recipe
To make the crispy onion puff pastry, here’s what you’ll need.
Puff pastry: Puff pastry serves as the base for these delicious onion tarts. You should be able to find them in the frozen section of your supermarket.
White onion: White onions, when caramelized, bring an insanely delicious savory and umami flavor to the upside down tarts.
Balsamic vinegar: A dash of balsamic vinegar or balsamic glaze can bring some more depth of flavor and complexity to these puff pastry tarts.
Honey: I used a light drizzle of my homemade hot honey to jazz up the flavors in these tarts.
Gruyere cheese: Gruyere cheese, teamed up with the caramelized onions is what brings the perfect French onion flavor into these little tarts.
Egg: You’ll also need an egg to make a simple egg wash to coat the upside down tarts.
Thyme: The fragrant thyme brings a nice earthy and aromatic flavor to the tarts.
Chili flakes: I used red chili flakes to season the tarts, but you can totally choose to keep it simple with just salt and pepper.
See recipe card for quantities.
How to Make Upside Down Onion Tarts
Preheat oven at 400°F. Meanwhile, get the sliced onions and cheese ready and cut the puff pastry into rectangles.
In a large baking sheet lined with parchment paper, add a teaspoon of balsamic vinegar, some honey, a sprig of thyme and sprinkle some chili flakes in different sections.
Place a slice of onion on top of the puddle and then with the Gruyere cheese slices.
Top with puff pastry and brush with beaten egg.
Bake for 20 to 25 minutes until the onions caramelize and the top is golden brown.
Substitutions & Variations
- You can choose to use fresh or dried thyme- whatever you have at hand.
- Rosemary can also be another great addition to these cheesy tarts.
- If you’re looking to make a vegetarian version of these upside down tarts, skip the egg wash and just brush a little olive oil onto the puff pastry before you pop them in the oven.
- White onions are the best choice for this recipe, but if you’re not able to find them, red onions can work too.
You can also flatten the puff pastry if you want to. Press the pastry around the edges using a spatula before you bake them.
How to Store Leftover Onion Tarts
You can store your leftover caramelized onion tarts in an airtight container and then refrigerate them.
You can reheat these onion tarts in the oven. I wouldn’t recommend microwaving them, as it can really cause the puff pastry to become soggy.
Tips & Tricks to Nail the Recipe
- Remember to start off with thawed puff pastry. This will ensure that the pastry is cooked to perfection, and is easier to work with as well.
- You can also experiment with different types of ‘fillings’ for these upside down tarts. Mushrooms, garlic, bell peppers and cherry tomatoes are all great options worth trying out!
- Another great idea is to use shallots instead of onions, or even use some other kinds of onions of your choice.
- To add some extra flavor to these delicious puff pastry tarts, you can sprinkle some beef or mushroom bouillon powder onto the onion slices before you place the pastry on the top!
- Remember to allow them to cool down for a few minutes and run a knife under the tarts to remove them easily.
How to Serve Upside Down Onion Tarts
This upside-down onion tart is a show-stopping dish that’s sure, but you might want to take it to the next level by teaming it up with a nice dip too!
I also love drizzling some more hot honey and balsamic glaze over the top, right before serving!
If you’re not able to find Gruyere cheese, you can choose to use some creamy Brie or goat cheese instead! Cream cheese can also work in a pinch!
I would highly recommend using flaky puff pastry for this recipe. While you can try this recipe with any other kind of pastry too, you won’t be able to enjoy the same crispiness and layers of flaky goodness as you would with the traditional puff pastry.
Looking for other recipes like this? Try these:
Upside Down Onion Tarts
- 1 sheet puff pastry thawed
- 3 sweet onion thinly sliced
- 3 tablespoon honey
- 1 tablespoon balsamic vinegar
- 1 teaspoon chili flakes
- Fresh thyme leaves, salt, and black pepper to taste
- 18 pcs thinly sliced gruyere cheese or as needed
- 1 egg beaten
- Preheat oven at 400°F. Meanwhile, get the sliced onions and cheese ready and cut the puff pastry into rectangles.
- In a large baking sheet lined with parchment paper, add a teaspoon of balsamic vinegar, some honey, a sprig of thyme and sprinkle some chili flakes in different sections.
- Place a slice of onion on top of the puddle and then with the Gruyere cheese slices.
- Top with puff pastry and brush with beaten egg.
- Bake for 20 to 25 minutes until the onions caramelize and the top is golden brown.
- Don't leave food sitting out at room temperature for extended periods
- Never leave cooking food unattended
- Use oils with high smoking point to avoid harmful compounds
- Always have good ventilation when using a gas stove