Cook ground beef, onion, chili powder, cumin and garlic, in a large skillet with deep sides over medium-high heat, until browned.
Add beef broth, enchilada sauce and milk and bring to a boil.
Stir in the uncooked pasta and continue to cook, uncovered, until the pasta is al dente, 12-15 minutes, stirring occasionally.
Remove from the heat, stir in the cheese and let stand, covered, until the cheese is melted.
Serve with dollops of sour cream, sliced scallions and additional cheese, if desired.