The caramelized onion tart is my ode to the French onion soup that I love so much! I wanted to make a super simple portable version of the soup that would be a satisfying snack or even a light meal on its own. This tart recipe uses store bought puff pastry which makes it super simple and easy to whip this up. Looking for something nice and easy for a weekend snack or even an appetizer for your next dinner party? This is the recipe my friends.
French Onion Soup – The inspiration
As I mentioned earlier, I love French Onion soup which btw can be easily made vegetarian or vegan. I also really like that it comes sort of built in with bread and cheese. Thinking of that, I realized this is one dish that can be easily converted to a tart. Instead of the bread on top, the bread is on the base in the form of puff pastry. I decided to go with store bought for its convenience. I also incorporated a specific method to caramelizing onions which is almost hands off . That means you can go about doing other things while they are caramelizing and not worry about them burning!
I think a lot of people are put off from making the soup because it seems complicated and time consuming . It is far from the truth. I think the soup itself is an easy to make dish that’s just perfect for what seems like never ending winter. This tart is even easier I promise and its delicious!
Ingredients for making the caramelized onion tart
The ingredient list for this caramelized onion tart is super short and most of it should be pantry staples. The only thing that you might need to run out and buy would be the frozen puff pastry sheet. We need
- Yellow Onions
- Vegetable broth or Better than bouillon vegetarian paste
- Butter/ Vegan butter
- Thyme Sprigs
- Frozen Puff Pastry Sheet
- Gruyere cheese/ Vegan melting cheese
- White wine (completely optional)
The tart will be ready in an 1 or 1 1/4 hour. I know it sounds like a lot of time but most of this time is letting the onions cook down while the puff pastry is thawing. I would highly suggest getting a good puff pastry made of butter(if not doing the vegan version). It makes all the difference to this tart! Before you start prepping, remove the puff pastry from the freezer and set it on the kitchen counter for thawing. If you have left it to thaw in the fridge, let it sit there until you are ready to use it.
Making it vegan
It is extremely easy to make this vegan by replacing the puff pastry, butter and cheese with vegan versions. I have not seen any options for vegan gruyere cheese in my local markets but I would suggest trying it with vegan parmesan or any other melting non-dairy cheese of your choice.
The caramelization process
The secret to getting the onions perfectly caramelized is adding broth and covering the dish and letting it cook down. I remember coming across this technique on America’s Test Kitchen Youtube channel where they caramelized onions with water and thought it was genius. You cook the onions in some butter and thyme leaves for a few minutes.Then mix in the sugar, broth and keep it closed for 40 minutes or so before you see the onions completely cooked down. While testing, I added wine a few minutes before I turned off the stove. Although it tasted good, I much preferred the version with no wine.
If you are adding wine, I would suggest adding a couple of tablespoons and let it cook down 5-8 minutes before you turn off the stove. Another tip is keep the salt to minimum since it can easily overpower the caramelized onions.Also the cheese has salt in it so less salt the better.
Making the caramelized onion tart
Once the onions are ready, score the puff pastry sheet to make a border around it. Inside the border, spread the gruyere cheese. Now top with the onion mixture to ensure the surface is equally covered. Top again with cheese. I went light with the second round of cheese because I wanted the onions to show through well. Cook in the oven for 10-12 minutes at 400 deg F until the cheese has melted and the puff pastry has browned on the edges. The tart is best eaten right out of the oven. If you have leftovers, store in the fridge for a couple of days and heat it in the oven or air fryer at 275 deg F for 5 minutes until warm.
I am excited for you to try this recipe and the full recipe card is listed below. Let me know what you think by leaving a comment and rating below. Did you make any changes to it? If so, share what you did and how it went in our comments section or tag me on Instagram with #dillandthyme.
Looking for more tasty treats? Check out these recipes
Caramelized Onion Tart
- 1 Puff Pastry Sheet
- 2 Yellow Onions medium sized and sliced
- 11/2 cup Vegetable Broth sub with a spoon of Bouillon paste dissolved in a cup and half of water
- 3 sprigs Fresh Thyme sub with dry thyme
- 2 tbsp Butter
- 1 cup Gruyere Shreds
- 1 tbsp Cane Sugar
- 1/2 tsp Salt
- 2 tbsp Dry White Wine optional
- Remove the puff pastry sheet from the freezer to let it thaw or leave it in the fridge if it has been tawing in the fridge.
- Heat a frying pan to medium low and add the butter. Once the butter has melted, add thyme leaves from 2 sprigs of thyme or a tablespoon of dried thyme.
- After 30-45 seconds, add the sliced onions and sugar. Mix for a few seconds and let it cook for five minutes. Regularly mix the onions to ensure they don't burn.
- Add the broth in to the pan and mix well. Cover the frying pan and let it cook for 40-45 minutes. Check every 15 minutes or so to check how much liquid is left.
- When most of the liquid has cooked off, add the wine if you would like and cook for another 10 minutes while sautéing regularly.
- If you are kipping the wine, let the broth cook off completely. By this time the onions would have completely caramelized and browned. Turn off the heat and keep the cooked onions aside.
- Heat the oven to 400 deg F. Place the puff pastry sheet on a sheet pan and score with a knife to create a "border" around the sheet. Sprinkle half the gruyere cheese within this "border" .
- Spread the caramelized onions on top of the cheese. Sprinkle the remaining cheese on top of the onion layer. Bake in the oven for 10-12 minutes until the cheese has melted and the puff pastry has browned.
- Remove and slightly cool before topping with remaining thyme. The tart is ready to serve.