1. Cook beef and onion in heavy large skillet over medium heat until brown, stirring frequently, about 10 minutes. Pour off drippings. Add next 4 ingredients and cook 4 minutes, stirring frequently. Stir in bell peppers and salsa. (Can be prepared 1 day ahead. Cover and refrigerate. Rewarm over low heat before continuing.)
2. Whisk 2 eggs until well blended. Heat 1 tablespoon oil in nonstick skillet over medium-high heat. Pour eggs into skillet. Using spatula, lift edges of eggs as they cook, letting uncooked part run underneath until omelet is set. Spoon 1/2 cup meat filling over half of omelet. Sprinkle 1/3 cup cheese over. Slide out onto plate, folding omelet over filling. Keep warm, Repeat process for remaining 7 omelets, adding more oil to skillet as necessary. Top each with a dollop of sour cream.