Preheat your oven to 375°F (190°C). Gently press your pastry dough into

a round, fluted tart pan or deep pie dish. Trim any excess overhang

while keeping a clean decorative fluted edge. Place the crust into the

fridge to stay cold while preparing the filling.

Heat the extra virgin olive oil in a large skillet over medium-high heat.

Add the diced yellow onion and cook for 3 minutes until soft and

translucent. Toss in the chopped fresh baby spinach and stir for 2

minutes until completely wilted.

Transfer the hot spinach and onion mixture into a fine-mesh strainer.

Press down firmly with the back of a large spoon to squeeze out all

excess liquid. This keeps the bottom of your pastry crust perfectly crisp.

In a large mixing bowl, whisk the 4 large eggs until completely smooth.

Pour in the heavy cream, grated Parmesan cheese, salt, black pepper, and

the tiny pinch of ground nutmeg. Whisk vigorously until fully blended.

Retrieve your chilled pie crust. Scatter the thoroughly drained spinach

and onion mixture evenly across the bottom. Use a teaspoon to drop

small, distinct dollops of the whole-milk ricotta evenly over the

spinach layer. Slowly pour the egg custard over the ingredients, filling

the pastry crust up to just below the inner rim.

Bake on the middle oven rack for 40 to 45 minutes. The quiche is ready

when the fluted pastry turns crisp and golden, and the top forms a

beautifully deep browned, bubbly surface. The center should be set but

maintain a slight, tender jiggle when nudged.

Remove from the oven and let the quiche rest on a wire cooling rack for

15 to 20 minutes. This allows the internal custard layers to firm up,

ensuring perfectly clean, sharp, beautiful slices.