Preheat oven to 350 degrees. Grease a 9 inch pie pan with non stick cooking spray.Heat butter in a large skillet over medium high heat. Add in onion and cook for 3-4 minutes or until tender and slightly browned.
Add in spinach and cook until wilted. Add in garlic and cook for an additional minute.
Transfer spinach onion mixture to a medium bowl along with heavy cream, eggs, cheese, salt and pepper. Stir to combine.
Pour egg mixture into the prepared pie pan and bake for 30-40 minutes or until the quiche looks set.
Allow it to cool for 5-10 minutes then slice and serve!
