Preheat the oven

• Preheat the oven to 200 °C.

Prepare the pastry base

• Line the baking tray with the puff pastry and prick it with a fork.
• Brush the surface with the mustard, leaving a border.

Arrange the tomatoes

• Scatter the grated cheese over the mustard.
• Arrange the tomato slices in overlapping rows.
• Drizzle with the olive oil and season with the oregano, salt and pepper.

Bake the tart

• Bake until the pastry is golden and the tomatoes are tender.

Serve

• Let the tart cool slightly, then slice and serve.