Onion Tart With Puff Pastry and Gruyere Cheese

This Onion Tart with Puff Pastry and Gruyere Cheese is made from a combination of puff pastry, caramelized onions, and Gruyere cheese. Ready in just one hour and it is perfect for any occasion.

This puff pastry tart, loaded with caramelized onions and Gruyere cheese is a perfect mix of sweet onions and nutty cheese, and everything is covered in a flaky crust.

In just an hour, you can whip up this elegant yet easy appetizer that fits any event, whether it’s a fancy party or a relaxed evening at home.

I’ll guide you through making this savory tart, showcasing how top-notch ingredients come together in a dish that’s as delicious as it is beautiful. It’s sure to become a favorite in your kitchen.

Let’s get started!

🥘 Ingredients and Substitutes

• Puff Pastry. I start with puff pastry for the tart because it’s flaky and turns perfectly golden when baked. If you can’t find it, layering phyllo dough with butter works too, though it’s a bit lighter.
• Onions. I use onions for their sweet depth once they’re caramelized – they’re really the star of the show. I prefer shallots for their subtle flavor and how they look in the tart, but any onion works.
• Honey A bit of honey brings out the onions’ sweetness and balances the savory taste. If you don’t have honey, maple syrup or even a sprinkle of sugar does the trick.
• Balsamic Vinegar. I splash in some balsamic vinegar for a tangy kick that makes the flavors pop. If you don’t have it, apple cider or red wine vinegar can swap in and still taste great.
• Gruyere Cheese makes everything come together with its nutty, melty goodness. Can’t find Gruyere? Emmental, Swiss, or a good sharp Cheddar are all fine substitutes.

👩‍🍳 Step-by-step Directions

First, peel and halve the onions. Use a non-stick pan that’s oven-safe, or start with a stove-top pan and switch to a baking dish later.

Melt half the butter with a teaspoon of olive oil in the pan on low heat. Place the onions cut side down, covering the pan. Arrange them however you like; I sometimes make a flower pattern.

Drizzle with honey and balsamic vinegar, season with a pinch of salt, then cover and simmer for 7 minutes.

Flip the onions carefully, add the rest of the butter, cover, and cook for another 8 minutes on low.

Meanwhile, preheat your oven to 400°F (200°C).

Flip the onions back, cut side down, keeping any pattern intact, and turn off the stove.

Lay the puff pastry over the onions, poking two holes in the center for venting.

Bake for 15-20 minutes until the pastry is golden.

To serve, invert the tart so the onions are on top.

You can leave it as is for a fancy look or go for a rustic vibe by sprinkling cheese over the hot tart and putting it back in the oven just until the cheese melts.

Serve hot to get the full experience of the sweet, sour, and creamy flavors.

🍽️ Serving Suggestions

• Pair the tart with a simple, fresh salad to cut through its richness. Think mixed greens—arugula, spinach, or baby kale—with a light vinaigrette and some toasted nuts for crunch.
• For soup, try a smooth tomato bisque or roasted pumpkin soup. The creamy texture contrasts well with the tart, making for a cozy meal when it’s cold out.
• If you want to make the tart heartier, top it with prosciutto, crispy bacon, or smoked salmon before serving. These add a savory depth, perfect if you’re serving the tart as the main dish.
• Sprinkle fresh herbs like thyme, chives, or basil on top before serving for a burst of freshness and color. They add a nice aroma that goes well with the onions and cheese.

🍲 Storage

In the Refrigerator:

Cool the tart to room temp before you stash it in the fridge. This keeps the crust from getting soggy. Wrap it up tight in plastic or foil, or use an airtight container to keep it fresh and stop it from picking up weird fridge smells. It’ll last like this for about 3 days.

In the Freezer:

Wrap the cooled tart in plastic and then foil, or pop it in a freezer bag or container to keep freezer burn at bay. You can freeze it for a couple of months without it tasting weird or getting a funny texture.

Considerations

• The crust is crispiest when it’s fresh. Freezing or fridging changes the texture a bit, but wrapping it well helps a lot.
• If you’re putting it in the fridge, maybe slip some parchment paper between the tart and the wrap to suck up any extra moisture.

Thawing and Reheating:

• Thaw it in the fridge overnight if it’s been frozen. Room temp thawing messes with the texture.
• Reheat it in the oven at 350°F (175°C) for about 10-15 minutes to get it warm and crispy again. Microwaves turn the crust soggy, so maybe don’t do that.

🏆 Expert Tips. What to Pay Attention To?

• Caramelizing Onions: Take your time cooking the onions on low heat, stirring now and then. This slow cook lets their sugars caramelize without burning, giving you a tasty base for the tart. A little honey and balsamic vinegar can boost the sweetness and add depth to the flavor.
• Keep the Pastry Cold: Make sure your puff pastry is nice and cold before you start. If it gets warm, it’s a pain to work with and might not puff up right. For a great-looking and tasting appetizer, leave the pastry in the fridge until you’re ready to put everything together.
• Baking It Right: Heat your oven up before baking the tart. A properly hot oven is key for getting that puff pastry to rise and turn golden. Placing the tart on the lower rack helps get a crispy bottom and cooks it through evenly.
• Let It Rest: Give the tart a few minutes to cool down after baking before cutting into it. This little break lets the flavors come together and makes it easier to slice without falling apart, showing off your puff pastry’s layers and filling.

📋 Recipe Card: