Preheat your oven to 350°F (175°C).

Place your unbaked pie crust in a 9-inch pie plate. If using a frozen crust, allow it to thaw for about 10 minutes before proceeding.

In a skillet over medium heat, melt the butter. Add chopped onions and sauté until translucent, about 3-4 minutes.

Add broccoli florets to the skillet and cook for another 2-3 minutes until they turn bright green but remain crisp. Remove from heat and let cool slightly.

Sprinkle half of the mozzarella and cheddar cheeses evenly over the bottom of the pie crust.

Spread the broccoli and onion mixture over the cheese layer.

In a medium bowl, whisk together eggs, half-and-half, salt, pepper, garlic powder, and nutmeg if using.

Pour the egg mixture over the broccoli layer, then sprinkle the remaining cheese on top.

Bake in the preheated oven for 45 minutes, or until the center is set and the top is golden brown.

Let the quiche rest for 10 minutes before slicing and serving.