While circular is the traditional shape, you can modify a tart to fit pretty much any bakeware.

 

Ingredients

Crust

• 1 1/4 cups all-purpose flour
• 1/2 cup freshly grated Parmesan
• 1/4 tsp freshly ground black pepper
• 1/2 cup chilled unsalted butter, cut in pieces
• 1/3 cup cold water

Filling

• 1 sweet onion, halved and thinly sliced
• Extra-virgin olive oil, for cooking and serving
• A few sprigs fresh thyme
• 1/4 cup basil pesto (optional)
• 4 oz soft goat cheese or Boursin garlic and fine herbs cheese
• 3 or 4 ripe heirloom tomatoes, sliced 1/4" thick
• Coarse sea salt
• A few pea shoots, for garnish

Directions

1 In a medium bowl (or the bowl of a food processor), combine the flour, Parmesan and pepper.

2 Add the butter and blend with a pastry blender or pulse in the food processor until the mixture resembles coarse meal. Add the cold water and stir by hand just until the dough comes together.

3 Shape the dough into a disc and let rest on the countertop for 20 minutes.

4 On a lightly floured surface, roll out the dough until it’s just larger than a 9" or 10" tart tin with a removable bottom. Fit the pastry into the tin and trim the edges until they’re flush with the edge of the tin. Refrigerate until chilled.

5 Preheat the oven to 375°F.

6 In a medium skillet, sauté the onion in a drizzle of oil over medium-high heat until golden, about 6 to 8 minutes. Pull the leaves off a sprig of thyme and add them during the last minute of cooking.

7 Spread the pesto over the bottom of the pastry crust, top with the caramelized onions, then crumble the goat cheese overtop.

8 Layer with the tomatoes, overlapping the slices. Drizzle with a bit more oil and sprinkle with salt.

9 Bake until the crust is golden and the tomatoes are tender, 35 to 40 minutes.

10 Cool to room temperature before garnishing with the pea shoots, slicing and serving.