Bring a large pot of lightly salted water to a boil and stir in macaroni from the packages, retaining cheese mix packets for later use.
Cook macaroni at a rolling boil over medium heat, stirring occasionally, until tender but still slightly firm, 8 to 10 minutes. Drain and rinse macaroni with cold water. Return cooked macaroni to the pot, (under cook as it continues in the soup!)
Mix butter, chicken broth, and tomatoes with macaroni and bring mixture to a simmer over medium heat; stir in garlic powder, onion powder,cumin, dry mustard, pepper, and contents of cheese mix packets.
Stir in milk and reduce heat to low; heat soup almost to a simmer. Do not boil.
Add cooked ground (taco) beef if you're using it! Stir in sour cream and serve.