Preheat oven to 200°C (400°F).

Put pastry base in your oven dish and prick with fork.

Slice tomatoes. Slice finely cheese.

Spread a generous layer of mustard. The spicy aftertaste of the Dijon mustard will disapear during baking.

Add a layer of cheese on top of the mustard and finish by a layer of tomatoes.

Dust thyme and pepper.

Bake for 30 minutes.