Preheat oven to 375
In cast iron skillet (12 inch), cook sausage until no longer pink. Drain grease.
Add chopped peppers and onions to sausage and cook until soft, 5-7 minutes. Then add spinach and give a stir.
In a medium bowl whisk together eggs, cream, salt, pepper and thyme. Then add in shredded cheese. Stir to combine.
Adjust heat for cast-iron to low-medium.
Pour egg mixture into the skillet. Quickly distribute sausage and eggs evenly.
Cook on stovetop, 3 -5 minutes. If sides get done, tip cast iron until uncooked eggs can run underneath cooked eggs.
Transfer to the oven and bake for 10 minutes.
Remove and sprinkle on feta cheese. Place under broiler for 3 minutes until just starting to brown and eggs are all cooked.
In another small bowl, toss together spinach, tomatoes, olive oil, salt and pepper.
Top frittata with salad and enjoy immediately.