Preheat oven to 350
Heat butter in a cast iron and add in chopped shallots
Caramelize shallots over medium heat and then add in chopped pepper
Add your spinach to wilt and precooked bacon
While that is cooking whisk your eggs, salt, pepper, and half & half in a small bowl
Pour egg mixture into cast iron and add in feta (save some to top frittata with after)
Mix together ingredients in pan to combine
Allow eggs to sit and crust start to form over medium heat (should take a few minutes)
Top with tomato slices
Once egg crust forms place in oven pan and bake for 18 minutes
Top with feta when done and enjoy!