Preheat oven to 400 degrees. Line pie crust with foil or parchment and weights. Bake 10 minutes. Remove weights and continue to bake for 2-5 minutes until pie crust begins to turn color and is set.
Set oven to 375 degrees.
Melt butter in a large pot, Add onion and cook over medium heat until soft, about 5 minutes. Chop damp spinach and add it to pan. Cover and cook, stirring occasionally until spinach is tender, about 5 minutes. Drain off any liquid in the pot, season with salt and pepper. Set aside.
In mixing bowl, whisk eggs and milk together. Stir in the spinach mixture and cheese.
Pour mixture into prebaked crust.
Place pie on a baking sheet and slide into oven. Bake until pie is golden brown , 35-40 minutes.
Remove from oven and let pie sit for approximatel;y 10 minutes before cutting.
Serve warm or room temperature.
