Thaw the Puff Pastry by allowing it to thaw in the refrigerator for about 30 minutes. Preheat your oven to 400°F (200°C).

Dust your work surface with flour and roll out each sheet of puff pastry to approximately 1/16 inch thick. Prick the pastry with a fork.

Cut out around 30 circles from the rolled pastry using a biscuit cutter. Arrange the circles on a parchment-lined baking sheet.

Sprinkle about 1 teaspoon of grated Gruyère cheese onto each puff pastry circle.

Layer thin slices of chosen tomatoes on top of the cheese.

Sprinkle each tartlet with kosher salt, ground black pepper, and chopped thyme.

Bake in the preheated oven for 20 to 25 minutes until golden brown and puffed.

Allow to cool slightly on a wire rack before serving.