Caramelized Onion Quick Tart (Printer-Friendly)

Rustic tart with rich caramelized onions and creamy Gruyère atop golden puff pastry.

# What You Need:

→ Pastry

01 - 1 sheet frozen puff pastry, thawed (approximately 8.8 oz)

→ Onions

02 - 3 large yellow onions, thinly sliced
03 - 2 tablespoons unsalted butter
04 - 1 tablespoon olive oil
05 - 1 teaspoon granulated sugar
06 - 1/2 teaspoon salt
07 - 1/4 teaspoon freshly ground black pepper

→ Filling & Topping

08 - 1/2 cup crème fraîche or sour cream (4 fl oz)
09 - 1 teaspoon Dijon mustard
10 - 1/2 cup grated Gruyère cheese (2.1 oz)
11 - 1 teaspoon fresh thyme leaves or 1/2 teaspoon dried thyme
12 - Optional: 1 tablespoon chopped fresh chives for garnish

# Directions:

01 - Preheat oven to 400°F. Line a baking sheet with parchment paper.
02 - In a large skillet over medium heat, melt butter with olive oil. Add sliced onions, sugar, salt, and pepper. Cook, stirring frequently, until onions are deep golden and caramelized, about 25 to 30 minutes.
03 - On a lightly floured surface, roll out puff pastry to a 12-inch square or circle. Transfer to the prepared baking sheet.
04 - Combine crème fraîche and Dijon mustard in a small bowl. Spread evenly over the pastry, leaving a 1-inch border.
05 - Scatter half the grated Gruyère over the crème mixture. Top with caramelized onions and sprinkle thyme leaves. Finish with the remaining Gruyère cheese.
06 - Gently fold the pastry edges over the filling to create a rustic border.
07 - Bake in preheated oven for 20 to 25 minutes, until pastry is golden and crisp. Allow to cool slightly before slicing.
08 - Optionally garnish with chopped fresh chives. Serve warm or at room temperature.

# Expert Suggestions:

01 -
  • It looks impressive but comes together with just a handful of ingredients you probably already have.
  • The slow cooked onions turn jammy and sweet, giving you that restaurant quality flavor at home.
  • You can serve it hot, warm, or even cold the next day straight from the fridge.
  • It works as a light dinner with a salad or sliced into small pieces for a party.
02 -
  • Dont rush the onions, if you crank the heat they will brown unevenly and taste bitter instead of sweet.
  • Leave that border on the pastry, it puffs up into a gorgeous golden frame and keeps the filling from spilling out.
  • Let the tart rest for five minutes after baking or the first slice will slide apart on you.
03 -
  • Use a sharp knife to slice the onions thin and even, it makes caramelizing faster and more consistent.
  • If your pastry is getting too dark before the filling is done, tent it loosely with foil for the last few minutes.
  • Taste the onions before you pile them on, if they need more salt or a pinch of sugar, add it then.
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