Preheat the oven to 375ºF. Melt the butter and brush the inside of an 8x8-inch casserole dish.
Roughly chop the spinach and slice the tomatoes in half. Sprinkle the spinach and tomatoes inside the casserole dish.
Crack the eggs into the casserole dish on top of the spinach and tomatoes. Season with the salt, pepper, and crushed red pepper. Drizzle the heavy cream over the eggs, then sprinkle the crumbled feta on top.
Transfer the casserole dish to the oven and bake for about 15 minutes, or just until the whites are set and the yolks are still liquid. (start checking around 10 minutes and add time as needed). Serve with crusty bread for dipping!
*You can use frozen spinach in place of fresh, just make sure to fully thaw and squeeze out the excess moisture first.**You can use any type of cheese you like, although creamier cheeses work best.To increase the servings to two eggs per person, simply keep all of the other ingredients the same and add 8 eggs to the dish instead of four. Baking time may increase.