Preheat oven to 350°F.
Melt the butter in a 10-inch oven-proof skillet over medium heat. 1 tablespoon butter
Add the red bell pepper and shallots. Season with a pinch of salt and pepper. Cook, stirring often, until slightly tender, about 3-5 minutes.
1 red bell pepper, 1 shallot, salt, pepper
Add the spinach and cook until wilted.
1 cup baby spinach
Spread the vegetables out into the bottom of the skillet.
In a medium bowl whisk the egg whites, heavy cream, salt and pepper until foamy.
8 egg whites, 2 tablespoons heavy whipping cream
Pour the egg mixture over the vegetables in the skillet.
Sprinkle the shredded cheese and cherry tomatoes evenly over the top.
1/2 cup cheddar cheese, 1/2 cup cherry tomatoes
Cook a minute or two until the bottom just starts to set.
Transfer the pan to the oven.
Cook 10-12 minutes or until the eggs are mostly set, but still slightly jiggly in the center. The eggs will set more as the frittata cools.
Garnish with fresh parsley, if desired.
parsley
Cut into 8 slices and serve.