Preheat oven to 350 degrees
Remove pie crust from freezer
Heat butter over medium heat in a saute pan
Saute onions until softened and translucent (3-4 min)
Add chopped spinach and toss quickly about 30 seconds. When spinach is wilted, remove from heat
In a bowl, whisk together eggs, half and half, salt and pepper
In pie crust, spread diced cheese across the bottom of the crust
Top cheese with veggies and finally pour over egg mixture
Place quiche on a rimmed baking pan and carefully place in oven
Bake at 350 or 40 minutes until a toothpick comes out clean or there's just a SLIGHT jiggle
Let quiche cool for 10 minutes before serving