Start by mixing flour and salt in a food processor. Add cold butter and pulse until crumbly. Slowly add ice water and vinegar until the dough forms. Shape into a disk, wrap, and chill to keep the crust flaky.
Slice the tomatoes and sprinkle with salt. Let them rest to release excess moisture. Pat them dry gently before assembling to avoid a soggy crust.
Combine goat cheese, olive oil, chives, thyme, garlic, and lemon zest in a bowl. Mix until smooth and creamy. This layer adds richness and balances the tomatoes.
Roll out the chilled dough into a large circle. Spread the goat cheese mixture in the center, leaving a border. Arrange tomatoes on top and fold the edges of the crust over the filling.
Brush the crust with the egg and water mixture. Bake in a preheated oven at 400°F until golden brown and crisp. Allow it to cool slightly before slicing.