In a large skillet, brown the beef and season with salt.
When the beef is browned, add onion, garlic, black beans, cilantro, serrano pepper, diced tomatoes and cumin.
Mix well and simmer on low, covered for 20 minutes.
Remove lid, add corn and simmer an additional 5 minutes or until all the liquid reduces.
Pre-heat oven to 350°F.
Cut peppers in half lengthwise, removing seeds and stem.
Place peppers, cut side up, in an oven-proof dish.
Fill each pepper with 1/2 cup beef mixture.
Pour about 1/3 cup water or chicken broth the bottom of the dish.
Cover tightly with foil.
Bake 45 – 50 minutes or until the peppers become soft.
Remove foil, top each with 1 1/2 tbsp. cheese and bake, uncovered, an additional 5 minutes.
Remove from oven, top with scallions and serve with reduced fat sour cream, if desired.
