Begin by preheating your oven to 400°F (200°C). Take the thawed puff pastry and gently roll it out on a floured surface until it is about an 1/8 inch thick. Carefully transfer the pastry to a tart pan, pressing it into the bottom and up the sides. Trim any excess pastry from the edges and prick the base with a fork to prevent bubbling while baking.
Next, heat a tablespoon of olive oil in a medium-sized skillet over medium heat. Add in the finely chopped onion and minced garlic, sautéing them until the onions become translucent and soft.
In a large mixing bowl, combine the pumpkin purée, ricotta cheese, eggs, half of the grated Parmesan, and the seasoning. Stir until the mixture is smooth and well combined.
Carefully pour the pumpkin filling into the prepared tart shell, spreading it out evenly with a spatula. Sprinkle the remaining Parmesan cheese on top for that extra layer of flavor and a beautiful golden crust as it bakes.
Once baked, remove the tart from the oven and let it cool for around 10 minutes before slicing.
Notes
Make ahead for better flavor, and store leftovers in an airtight container.