Preheat the oven to 400°F (200°C).

Unroll the puff pastry onto a parchment-lined baking sheet. If folded, gently unfold it on a lightly floured surface to prevent tearing.

Lightly score a 1-inch border around the edges using a knife, being careful not to cut all the way through. This helps the edges rise while keeping the center flat.

In a small bowl, mix ricotta, Parmesan, oregano, salt, and pepper until smooth. If the mixture is too thick to spread, add 1-2 teaspoons of milk or olive oil to loosen it.

Using a spoon or an offset spatula, spread the ricotta mixture evenly over the center of the pastry, staying inside the scored border.

For extra flavor, spread a thin layer of Dijon mustard over the ricotta.

Slice the tomatoes into thin rounds (or halve cherry tomatoes) and pat them dry with a paper towel to remove excess moisture. Arrange them in a slightly overlapping pattern over the ricotta mixture.

Drizzle olive oil over the tomatoes and season with salt and pepper.

In a small bowl, beat the egg with 1 tsp of water to make an egg wash. Brush the exposed edges of the pastry for a golden, glossy finish.

Bake for 20-25 minutes, or until the pastry is golden and crisp, and the tomatoes have softened and slightly caramelized around the edges. If the center still looks soggy, bake for an extra 3-5 minutes.

Let the tart cool for a few minutes before serving. Garnish with fresh basil or thyme, drizzle with extra olive oil if desired, then slice and serve warm or at room temperature.