Onion Tart
This upside down French onion tart layers puff pastry with caramelized onions, gruyere cheese, and fresh thyme for an easy, elegant appetizer that's perfect for a party.
Prep: 20 minutes
Cook: 30 minutes
Total: 1 hour
Servings: 9 to 12 squares
Ingredients
- 2 small/medium red onions
- 2 tablespoons extra-virgin olive oil
- 4 tablespoons honey or hot honey
- ½ teaspoon flaky sea salt plus additional for serving
- ½ teaspoon ground black pepper
- 6 to 8 sprigs fresh thyme plus fresh leaves for serving
- 3 ounces Gruyère cheese thinly sliced
- 1 sheet frozen puff pastry thawed according to package directions
- 1 large egg beaten with 1 teaspoon water to create an egg wash
- Balsamic glaze optional for serving
Instructions
- Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper.
- Peel the onions, then slice them crosswise 1/4-inch thick through the equator (not the ends) so that you create rings. I HIGHLY recommend a mandoline for easy, even slicing. Try to keep the layers in each slice together so you have onion "discs."
- Create 6 drizzle patches of olive oil spaced evenly over the parchment in 2 rows of 3 (see video for suggested placement).
- Drizzle the honey over the oil, then sprinkle each patch with a pinch of flaky salt and black pepper. Lay a small thyme sprig across each one.
- Find your largest onion discs and lay one over each patch. Then, take the smaller discs and fill in the gaps. Almost no parchment should peek through; a little overlap is fine.
- Lay the Gruyère slices over the onions, spacing them evenly and leaving a border of at least 1 inch on all sides.
- Unfold the puff pastry on a lightly floured work surface. Roll it into a rectangle about 2 inches longer than the onions on each side (mine was 10 by 13). Gently drape the pastry over the onions. With the tines of a fork, press the edges of the pastry all the way around to create a border.
- Brush the pastry lightly with the egg wash. Dab up any pools that collect with a paper towel.
- Bake the onion tart for 25 to 30 minutes on the center rack, until the pastry is deeply golden and puffed.
- Let rest 5 to 10 minutes. Set a large cutting board on top of the pan. Working quickly and confidently, flip the board and tart over together so the tart is now sitting on the board. Lift off the pan and peel away the parchment. Drizzle with balsamic glaze, scatter with fresh thyme leaves and flaky salt, and slice into squares.
Notes
- Don't stress over the tart being hot from the oven the moment you serve it. It tastes great at room temperature also.
- This tart tastes best the day it is made but can be stored in the refrigerator overnight. Rewarm in the oven, toaster oven, or air fryer at 375°F.
Nutrition
Serving: 1of 9 slicesCalories: 264kcalCarbohydrates: 23gProtein: 6gFat: 17gSaturated Fat: 5gPolyunsaturated Fat: 2gMonounsaturated Fat: 9gTrans Fat: 0.002gCholesterol: 31mgSodium: 274mgPotassium: 78mgFiber: 1gSugar: 9gVitamin A: 153IUVitamin C: 3mgCalcium: 111mgIron: 1mg
