Golden Onion and Gruyère Tart

1. Prepare the Tart Shell

Begin by rolling out your pie dough into a 12-inch round. Gently place it into a 9-inch tart or pie pan, folding the edges to create double-thick sides, and pressing them firmly against the pan. Prick the bottom with a fork, then refrigerate for at least 1 hour to ensure it holds its shape.

2. Blind Bake the Tart Shell

Preheat your oven to 375°F. Once the dough is chilled, line the shell with foil or parchment paper and fill it with dried beans or pie weights. This blind-baking step is crucial as it helps the crust bake evenly and prevents puffing. Bake for about 15 minutes, until the edges are lightly golden. Carefully remove the weights and bake for an additional 5 to 7 minutes until the entire shell is evenly light golden brown.

3. Caramelize the Onions

While the tart shell bakes, melt 4 tablespoons of butter in a heavy-bottomed skillet over medium heat. Add the sliced onions, seasoning with salt and fresh-ground black pepper. Cook the onions, stirring frequently, for 20 to 30 minutes until they are soft and golden. This caramelization process is key to developing a deep, rich flavor. Once done, spread the onions out to cool slightly.

4. Prepare the Custard Mixture

In a bowl, mix together 1.5 cups of half-and-half, 2 eggs, 2 egg yolks, 0.5 cup of grated Gruyère cheese, a pinch of cayenne, and a bit more salt and pepper to taste. This custard mixture will bind the tart together while adding a creamy texture.

5. Assemble and Bake the Tart

Spread the cooled onions evenly over the baked tart shell. Carefully pour the custard mixture over the onions, ensuring it fills all gaps. Place the assembled tart back into the 375°F oven and bake for 35 to 40 minutes, or until the top is puffed and lightly golden.

6. Cool and Serve

Allow the tart to cool slightly before slicing. Serve warm or at room temperature, enjoying the harmony of sweet onions and nutty Gruyère in every bite.