This late-season tomato tart is a fitting farewell to tomato season
6 to 7 tablespoons ice water
1 1/2 pounds mixed tomatoes, cored and sliced 1/4-inch thick
1 shallot, sliced thin
2 tablespoons extra-virgin olive oil
1 teaspoon minced fresh thyme
1 garlic clove, minced
1/4 teaspoon pepper
2 teaspoons Dijon mustard
3 ounces Gruyere cheese, shredded (3/4 cup)
2 tablespoons grated Parmesan cheese
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