Prepare all ingredients:
the puff pastry...
...and it in a tart mold.
Spread the complete surface of the pastry...
...with hot mustard.
Place the finely sliced emmental on top.
Slice the tomatoes in rounds...
...and place them on the emmental.
Sprinkle the surface of the tart with oregano and add a drizzle of olive oil. add salt and pepper.
Bake in hot oven, 200°C for 25 to 30 minutes.
When finished, remove the tart from the oven. Leave to cool slightly before serving.