Combine flour, cornmeal, salt, and sugar in the bowl of a food processor. Pulse very briefly to combine. Add the cold, cubed butter and pulse until the size of small peas. Slowly add the ice water while pulsing. Stop when the dough just starts to come together.

Transfer the tart dough mixture to a sheet of plastic wrap. Press the dough into a disk and wrap completely in the plastic. Refrigerate for at least 2 hours.

Remove tart dough from the refrigerator. Roll dough between a lightly-floured sheet of waxed paper and plastic wrap to a 1/8-inch thickness. Transfer rolled dough to tart pan and trim edges. Place in freezer.

Preheat oven to 400˚F. Line tart shells with foil and fill with dried beans or rice. Place tart pans on a rimmed baking sheet and bake on the middle rack of oven for 18 minutes. Remove foil and beans/or rice and return tart shells to oven. Continue to bake until shells are a light golden. Remove from oven.

In a medium-size bowl, whisk together the eggs, heavy cream, milk, and green onions. Season with salt and pepper.

Spread half the goat cheese evenly over the bottom of the tart, followed by the zucchini and onions. Slowly pour the egg mixture over the tarts, filling just below the rims. Place the tomato slices over the top of the egg mixture and the other and then top with the remaining goat cheese.

Place the filled tart shells on rimmed baking sheet in the center of the 375˚F oven and bake for approximately 25 minutes, until custard has set and tomatoes are starting to shrivel.

Remove from oven and eat either warm or at room temperature.