2 tablespoons olive oil 
4 cups lean steak strips or 4 cups chicken breast strips 
1 tablespoon chipotle pepper (or to taste) 
1 cup thinly sliced green bell peppers 
1 1/2 cups thinly sliced onions 
1 tablespoon minced garlic 
2 tablespoons lemon juice 
10 large flour or corn tortillas 
2 cups basic red sauce or prepared salsa 
1 pint sour cream 
2 cups shredded extra-sharp Cheddar cheese
Salt, to taste (optional)