In a medium saucepan, combine refried beans, tomatoes, salsa, cheddar cheese, taco sauce, and chilies. Stir over medium heat until thoroughly combined, about 3 to 5 minutes. Stir in the juice of 1 lime. Simmer and cover until ready to serve.
For the meat:
Brown ground beef and onion until beef is no longer pink and onion is translucent. Drain excess fat and return to the stove on low heat. Add the tomato sauce, chili powder, cumin, salt, oregano, garlic powder, and green chiles. Stir and simmer for 2 minutes.
Heat taco shells according to package directions.
Assemble tacos:
Spoon meat filling into taco shells. Top with bean mixture, lettuce, cheese, fresh cilantro, and/or sour cream.