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This caramelized onion tart transforms simple ingredients into a sophisticated appetizer that never fails to impress dinner guests. The combination of sweet, jammy onions with tangy blue cheese creates a flavor profile that's both comforting and elegant—perfect for everything from holiday gatherings to casual wine nights.
I first made this tart for a last-minute dinner party when I had nothing but onions and cheese in my refrigerator. What started as a desperate solution has become my most requested recipe, earning its place at every holiday gathering.
Ingredients
- Extra virgin olive oil: Creates the foundation for properly caramelizing onions, giving them their rich flavor
- Onions: Sliced root-to-top ensures they maintain their structure while cooking down into sweet, jammy perfection
- Brown sugar: Accelerates the caramelization process, bringing out natural sweetness
- Balsamic vinegar: Adds complexity and a subtle tangy note that balances the sweetness
- Frozen puff pastry: Provides a buttery, crisp base with no fussing with homemade dough
- Brie cheese: Creates a creamy, melty texture once baked; always remove the rind for smoothest results
- Gorgonzola cheese: Provides sharp, tangy contrast to the sweet onions; seek out a creamy variety for best melting
- Fresh tarragon: Brings an unexpected anise flavor that elevates this tart beyond ordinary; choose bright green bunches for maximum flavor
Step-by-Step Instructions
- Caramelize the Onions:
- Heat olive oil in a large, deep pan over medium-high heat until shimmering. Add sliced onions and cook for 10 minutes, stirring occasionally until softened and golden. Sprinkle brown sugar evenly over onions, followed by balsamic vinegar, salt, and pepper. Reduce heat to medium-low and cook uncovered for 20-25 minutes, stirring occasionally until onions become a jam-like consistency. If the pan appears dry, add a tablespoon of water to prevent burning. Remove from heat and let cool completely.
- Prepare the Pastry:
- Preheat oven to 400°F with rack in the middle position. Gently unfold defrosted puff pastry onto a parchment-lined baking sheet. Using a rolling pin, roll into a rectangle approximately 10-by-14 inches. Prick the surface of the dough with a fork at 2-inch intervals to prevent bubbling and ensure a crisp base.
- Assemble the Tart:
- Spread the cooled caramelized onions evenly over the pastry, ensuring it reaches the edges. Distribute diced brie and gorgonzola cheese evenly over the top. Sprinkle fresh tarragon leaves over everything.
- Bake to Golden Perfection:
- Bake the tart in the preheated oven for 18-20 minutes, rotating the pan halfway through. The tart is done when the edges are puffed and deep golden brown, and cheeses are fully melted. Remove from oven and rest for 5 minutes before slicing.
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The tarragon in this recipe is my secret weapon. I discovered its magic after substituting it for thyme when my herb garden failed me one summer. The licorice notes create an unexpected complexity that makes guests wonder about your secret ingredient. My neighbor actually stood in my kitchen refusing to leave until I revealed what made it taste so special.
Make-Ahead Magic
This tart shines as a prepare-ahead dish perfect for entertaining. You can caramelize the onions up to three days in advance, keeping them refrigerated in an airtight container. The entire tart can be assembled and refrigerated unbaked for up to 24 hours. Simply add an extra 2-3 minutes to the baking time if cooking directly from refrigeration. For last-minute gatherings, I often keep a roll of puff pastry in the freezer and jars of caramelized onions in the refrigerator ready for unexpected guests.
Perfect Pairings
The rich, savory flavors of this tart call for brightness to balance each bite. Serve alongside a crisp green salad dressed with a simple lemon vinaigrette. For wine pairings, reach for something with enough acidity to cut through the richness—a Sauvignon Blanc or unoaked Chardonnay works beautifully. If serving as an appetizer, consider slicing into small two-inch squares and topping each with a tiny sprig of fresh tarragon for an elegant presentation at cocktail parties.
Troubleshooting Tips
When working with puff pastry, timing is everything. Keep the pastry refrigerated until absolutely ready to use. If it becomes too warm, it will become sticky and difficult to handle. Should this happen, simply return it to the refrigerator for 15 minutes before proceeding. For the crispest base, blind bake the pricked pastry for 5 minutes before adding toppings if serving to a large crowd. This ensures the center remains crisp even when sitting out during a party.
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This caramelized onion tart melts hearts and elevates gatherings with its irresistible sweet and savory flavors.
Frequently Asked Questions
- → Can I make this caramelized onion tart ahead of time?
Yes! You can caramelize the onions up to 3 days in advance and store them in the refrigerator. You can also assemble the entire tart and refrigerate it for up to 24 hours before baking. Just add an extra 2-3 minutes to the baking time if cooking from cold.
- → What can I substitute for tarragon in this tart?
If you don't have tarragon, try using fresh thyme, rosemary, or basil. Each will provide a different flavor profile, but all work well with the caramelized onions and cheese combination.
- → How do I serve this onion and cheese tart?
This tart is versatile! Serve it warm as an elegant appetizer cut into small squares, as a main course alongside a simple green salad, or at room temperature for a picnic or brunch. It's also wonderful as part of a cheese board.
- → Can I use different cheeses in this tart?
Absolutely! While Gorgonzola and Brie offer a perfect balance of sharp and creamy, you can substitute with other cheese combinations. Try gruyère for nuttiness, fontina for meltability, or even goat cheese for tanginess. Just maintain a balance of flavors.
- → Why do I need to prick the pastry with a fork?
Pricking the puff pastry with a fork before baking (called docking) prevents large air bubbles from forming during baking. This ensures an even surface for your toppings and helps the pastry bake evenly.
- → How can I tell when my onions are properly caramelized?
Properly caramelized onions should be deeply golden brown (not burnt), very soft, and significantly reduced in volume. They'll have a sweet, rich flavor with none of the sharp bite of raw onions. This process takes patience - about 25-30 minutes of gentle cooking.