Prep time: 20 min | Cook time: 20 min | Ready In: 40 min
4 tablespoons butter
2 large onions, halved and thinly sliced
salt & pepper, to taste
pie dough (store bought or homemade)
1-1/2 cups monterey jack cheese, grated
1/4 cup parmesan cheese, grated
1/4 cup swiss cheese, grated
3 cups cherry tomatoes
1 large egg
1/4 cup milk
16 basil leaves, roughly chopped
Heat a large skillet over medium heat. Add the butter, onions and salt & pepper. Cook, stirring occasionally, until the onions get soft and golden brown, 5-7 minutes. Then set them aside.
Preheat oven to 450 degrees.
Roll out the pie dough into a large, thin rectangle and lay over a shallow 9-by-13 inch baking sheet, pressing dough into the corners.
Mix the cheese together and spread over the crust in a single layer. Arrange the golden onions over the cheese, then arrange the tomatoes in a single layer on top of that.
Combine the egg and milk in a small bowl and whisk with a fork. Tuck the edges of the crust under themselves, then brush the entire edge of the crust with the egg mixture.
Bake the tart for 15-18 minutes, watching carefully to be sure the crust doesn’t burn.
Let the tart sit for 5 minutes before serving. Sprinkle the basil on top and cut into large squares to serve.