In a mixing bowl, combine the flour with a pinch of salt. Add the cold butter and use your fingers or a pastry cutter to work it into the flour until the mixture resembles coarse crumbs.
Gradually add ice water, one tablespoon at a time, mixing gently until the dough begins to come together. Be careful not to overmix; the dough should be crumbly but hold together when pressed.
Gather the dough into a ball, flatten it slightly into a disk, wrap in plastic wrap, and refrigerate for at least 30 minutes to relax the gluten and keep it flaky.
Once chilled, remove the dough from the fridge and lightly flour a clean surface. Roll out the dough into a 12-inch circle, aiming for an even thickness, and transfer it to a parchment-lined baking sheet.
Place the rolled-out dough in the freezer for 10 minutes to firm up, which helps prevent shrinking during baking.
While the dough chills, gently blot the sliced heirloom tomatoes with paper towels to remove excess moisture. This step helps prevent sogginess in the tart.
Preheat your oven to 375°F (190°C). Remove the dough from the freezer and spread crumbled cheese evenly over the surface, leaving a 2-inch border around the edges.
Arrange the drained tomato slices on top of the cheese, overlapping slightly and gently blotting any remaining moisture if needed. Season with flaky sea salt and freshly cracked black pepper.
Fold the edges of the pastry border over the filling, pleating slightly to create a rustic edge. Drizzle the entire tart with olive oil for shine and flavor.
Bake the tart in the preheated oven for about 35-40 minutes, until the crust is golden and crispy, and the tomato edges are blistered and slightly caramelized.
Remove the tart from the oven and immediately sprinkle with chopped basil for a fresh burst of flavor. Let it cool slightly before slicing and serving.
