In a large skillet over medium heat, add diced bacon and cook until crispy, about 5–7 minutes.

In the same skillet, add thinly sliced sweet onions, seasoning with kosher salt and black pepper. Cook over medium-low heat for 25–30 minutes, until deeply golden.

Preheat your oven to 400°F (200°C). Roll out the frozen puff pastry and place it on a baking sheet, scoring a 1-inch border.

In a mixing bowl, blend together ricotta cheese and pumpkin purée until smooth. Spread the mixture on the pastry, layer with onions and bacon, and top with mozzarella.

Scatter fresh sage leaves over the filling and brush exposed edges with an egg wash. Bake for 25–30 minutes until puffed and golden.

Let the tart cool for a few minutes, then sprinkle with grated Parmesan cheese and serve warm or at room temperature.