Make the crust by combining the butter, flour, and salt in a food processor until it resembles coarse crumbs.
Add the cold water and pulse until the dough just begins to come together.
Turn the dough out onto a lightly floured surface and shape into a disk. Wrap in plastic and refrigerate for at least 30 minutes.
Preheat the oven to 400°F.
On a lightly floured surface, roll the dough out to ⅛-inch thickness.
Cut out 4-inch rounds using a biscuit cutter or the rim of a glass.
Place the rounds on a parchment-lined baking sheet.
Top each round with sliced heirloom tomatoes, leaving a 1-inch border.
Fold the edges of the dough over the tomatoes, overlapping slightly.
Bake for 20-25 minutes, until the crust is golden brown.
Serve warm, garnished with fresh basil if desired.
