Prep Work

Cup of Yum
1. Slice the onions and cook on medium-high heat with the butter stirring occasionally. Reduce the heat to medium or medium-low if the onions start to burn. Slow cooking breaks down the sugars in the onions and this takes a while (30-40 min).
2. Slice the tomatoes. Cherry tomatoes can be halved. Larger tomatoes should be sliced into 1 inch pieces. Toss with 2 tablespoons olive oil, 1/4 tsp kosher salt and thyme if desired.

For the Pastry Dough

1. Mix the flour and salt in a bowl.
2. Grate the butter into the flour mixing as you go.
3. Add 2 tbs of the ice water (you can add more later if need be) and work the dough together for just a few moments more until it comes together.
4. Add another 1/2 to 1 tbs ice water if it's too dry or crumbly.
5. Separate, gently flatten the dough into a disk and cover in plastic wrap.
6. Place in the fridge. and let the dough chill for at least 30 minutes.

For the Assembly

1. Preheat oven to 450F
2. In a small bowl, lightly beat the egg with a teaspoon of water.
3. Roll the dough out and press into a large tart pan.
4. Spread the goat cheese on the base.
5. Arrange the caramelized onions on top then cover with tomatoes cut side up.
6. Brush edge with egg wash
7. Bake for about 15 minutes or until crust is golden brown and tomatoes have softened.