Tomato, chard and egg white frittata

(There's going to be a lot of tomato recipes on here. Just bear with me.)

This was actually far tastier than I thought it would be. I thought, you know, egg white frittata, some oven-roasted cherry tomatoes, some swiss chard, some random bits of vegetables, it would taste like egg whites with vegetables. But this was really good.

Caveat: you'll need a cast-iron skillet for this, or some other kind of skillet that can go directly from stovetop to oven.

5-6 egg whites
2 whole eggs
a handful of cherry tomatoes (either fresh or roasted)
1 shallot, sliced
3 leaves of swiss chard, chopped
1/3 cup crumbled feta cheese

Saute the shallot in a couple tablespoons of either olive oil or bacon fat (I used bacon fat) until soft. Add the swiss chard, and cook just until wilted. Mix together the egg whites, eggs, and feta cheese, and pour into the pan with the swiss chard. Mix together, and add the cherry tomatoes (I also threw in a few green beans). Bake at 425 for 15-20 minutes or until puffy and browned on top. Salt and pepper to taste.