This caramelized onion tart is an elegant yet incredibly simple dish made with just a handful of pantry staples. Sweet, tender onions baked beneath a flaky puff pastry create a savory tart that feels special enough for entertaining while remaining approachable for beginner cooks.
Why You’ll Love This Recipe
This recipe delivers maximum flavor with minimal effort and ingredients. The natural sweetness of slowly cooked onions pairs beautifully with the tangy depth of balsamic vinegar and maple syrup. Baking the tart upside down ensures a crisp, golden pastry while allowing the onions to caramelize to perfection. It’s versatile enough to serve as an appetizer, light lunch, or elegant dinner starter, and it looks far more impressive than the time and cost involved.
Ingredients
(Tip: You’ll find the full list of ingredients and measurements in the recipe card below.)
200 grams puff pastry, 1 sheet, thawed
4 medium red onions, sliced into ½-inch-thick rounds
1 tablespoon balsamic vinegar
1 tablespoon maple syrup
1 teaspoon salt
1 tablespoon olive oil (optional, for added richness)
Fresh thyme leaves, optional for garnish
Directions
If using frozen puff pastry, thaw it according to the package instructions and keep it chilled until ready to use.
Peel the onions and slice them into thick rounds, about ½ inch in thickness.
Heat a large pan over medium heat. Arrange the onion slices evenly in the pan.
Pour in enough boiling water to fully cover the onions. Reduce the heat to medium-low and let them simmer for about 20 minutes, or until the water has completely evaporated and the onions are tender.
Add the balsamic vinegar, maple syrup, salt, and olive oil if using. Cook for a few more minutes, allowing the onions to caramelize lightly and develop a golden-brown color. Remove from heat.
Preheat the oven to 400°F (200°C). Lightly grease an 8.5 x 10-inch pie or tart pan with oil.
Transfer the caramelized onions into the pan, spreading them evenly across the bottom.
Lay the puff pastry sheet over the onions, tucking the edges gently around them.
Bake for 30 minutes, or until the pastry is puffed and deeply golden.
Remove from the oven and allow the tart to cool for a few minutes. Carefully invert it onto a serving platter or cutting board.
Garnish with fresh thyme if desired. Slice and serve warm.
Servings and timing
This recipe makes 4 servings.
Prep time: 5 minutes
Cooking time: 50 minutes
Total time: approximately 55 minutes
Variations
Swap red onions for yellow or sweet onions for a milder flavor.
Add thinly sliced cooked vegetables such as carrots, potatoes, or Brussels sprouts alongside the onions.
Replace maple syrup with brown sugar, coconut sugar, or date syrup for a slightly different sweetness.
Use apple cider vinegar instead of balsamic vinegar for a brighter, lighter tang.
Storage/Reheating
Store leftover tart in an airtight container in the refrigerator for up to 3 days. To reheat, place slices in a preheated oven at 350°F (175°C) for 8–10 minutes until warmed through and the pastry regains its crispness. Avoid microwaving, as it can make the pastry soggy.
FAQs
Can I make this tart ahead of time?
Yes, you can prepare and bake the tart a day in advance. Reheat it in the oven before serving for best texture.
Is puff pastry always vegan?
Many store-bought puff pastries are made with vegetable fats, but always check the ingredient list to be sure.
Can I use frozen onions?
Fresh onions are recommended for the best texture and flavor, as frozen onions release more moisture.
What pan size works best?
An 8.5 x 10-inch pie or tart pan works well, but a similar-sized oven-safe dish will also work.
Can I make this recipe gluten-free?
Yes, substitute the puff pastry with a gluten-free pastry that can withstand baking.
Why is the tart baked upside down?
Baking it upside down ensures the pastry stays crisp while the onions caramelize beautifully.
Can I add herbs other than thyme?
Yes, rosemary or oregano can be used, but thyme pairs especially well with onions.
How do I prevent the tart from sticking?
Grease the pan well with oil and allow the tart to cool slightly before flipping.
Can I serve this cold?
It’s best served warm, but it can also be enjoyed at room temperature.
Is this suitable as a main dish?
It works best as an appetizer or light meal, but you can pair it with a salad for a more filling option.
Conclusion
This caramelized onion tart proves that simple ingredients can create truly memorable dishes. With its flaky pastry, rich onion filling, and balanced sweet-and-savory flavor, it’s a recipe you’ll return to again and again for both casual meals and special occasions.
This caramelized onion tart features tender, sweet onions baked beneath golden puff pastry for a savory, elegant dish that’s simple to prepare and full of flavor. Perfect as an appetizer, light lunch, or stylish starter.
Ingredients
200 grams puff pastry, 1 sheet, thawed
4 medium red onions, sliced into ½-inch-thick rounds
1 tablespoon balsamic vinegar
1 tablespoon maple syrup
1 teaspoon salt
1 tablespoon olive oil (optional)
Fresh thyme leaves, optional for garnish
Instructions
Thaw puff pastry according to package instructions and keep chilled until ready to use.
Peel and slice the onions into ½-inch-thick rounds.
Heat a large pan over medium heat. Arrange onion slices evenly in the pan and cover with boiling water. Simmer on medium-low heat for about 20 minutes until water evaporates and onions are tender.
Add balsamic vinegar, maple syrup, salt, and olive oil (if using). Cook for a few more minutes until lightly caramelized and golden. Remove from heat.
Preheat oven to 400°F (200°C). Lightly grease an 8.5 x 10-inch tart or pie pan.
Spread the caramelized onions evenly across the bottom of the pan.
Lay the puff pastry over the onions, gently tucking the edges around them.
Bake for 30 minutes or until pastry is puffed and deeply golden.
Let tart cool for a few minutes, then carefully invert onto a serving plate or board.
Garnish with fresh thyme if desired. Slice and serve warm.
Notes
Use yellow or sweet onions for a milder flavor.
Add other cooked vegetables like carrots or potatoes.
Swap maple syrup with brown or coconut sugar.
Use apple cider vinegar instead of balsamic for a lighter tang.
Reheat in the oven to retain pastry crispness—avoid microwaving.
