1) To make the crust: Put the flour in a bowl, or in the work bowl of a food processor. Add the cream cheese, salt, and buttermilk powder. Mix together until everything is evenly crumbly. If you're using a food processor, just a few quick pulses are all you'll need.
2) Cut the cold butter into pieces and work it into the flour, leaving some visible pieces.
3) Sprinkle the dough with the cold water and toss. Squeeze the dough to determine if it holds together. If it's too dry, add water 1 tablespoon at a time, using just enough so the dough will hold together.
4) Divide the dough in half, to make two 9" tarts. Or divide it in eight pieces, to make eight 4 1/2" tarts. Or make one full-sized tart, and four small tarts. Flatten each piece of dough into a disk, wrap well, and refrigerate for 30 minutes or longer.
5) If you're making two large tarts, roll each piece of dough to a 12" diameter. For small tarts, roll each piece to a 5 1/2" to 6" diameter.
6) Gently place the rolled-out pastry in the tart pan, smoothing it over the bottom and tucking it into the sides. Roll your rolling pin across the top of the pan to cut off the excess pastry. Peel the pastry away from the edge of the pan. You can bake these trimmings along with the tarts, for a crunchy/flaky snack.
7) If you're making small tarts, prick the bottom crust all over with a fork. Bake them in a preheated 350°F oven for 10 minutes; they'll probably puff up a bit, despite the pricking; and their sides will slide down the edges of the pan. That's OK. Remove the tarts from the oven, and set aside while you make the filling.
8) If you're making two 9" tarts, refrigerate the crusts while you prepare the filling.
9) To fill the mini tarts: Place about 8 cherry tomato halves in the bottom of each tart shell. Sprinkle each tart with 2 tablespoons of your favorite shredded cheese; we like a combination of blue cheese and cheddar.
10) Bake the tarts in a preheated 425°F oven for about 20 minutes, till their crusts are brown and the cheese is melted. Remove from the oven, and serve warm, or at room temperature.
11) To fill the standard tarts: Whisk together the eggs, milk, cheese, herbs, and salt. Divide the mixture between the two chilled shells. Lay the sliced tomatoes on top.
12) Bake in a preheated 425°F oven for 15 minutes, then reduce the oven temperature to 350°F and bake for another 10 to 15 minutes, till the crust is brown and the custard is set. Remove from the oven, and serve warm.
Yield: 2 large or 8 small tarts.