Preheat oven to 350 degrees F. Combine tuna, red pepper, corn and green onions in a bowl. Combine salsa, sour cream and cumin in small bowl. Gently stir salsa mixture into tuna.
Wrap flour tortillas in aluminum foil. Heat in 350 degree F oven for 10 minutes.
Coat outside of four 10-ounce custard cups with nonstick cooking spray. Invert onto baking sheet.
Remove tortillas from oven. Increase oven temperature to 400 degrees F. Place 1 tortilla at a time (keep remaining ones wrapped in foil) on prepared custard cup, pressing gently to shape.
Bake tortillas in 400 degree F oven 10 minutes. Remove baked shells to rack to cool completely.
Line tortilla cups with lettuce. Fill each shell with the tuna mixture. Makes 4 servings.