Brown beef and onion in 6-quart Dutch oven over medium-high 8 minutes, crumbling finely, to 160°F. Spoon off excess fat.
Stir in garlic, chili powder, cumin, and paste; cook 1 minute.
Add beans, tomatoes with juices, broth, and salt; boil. Add macaroni; steadily simmer uncovered.
Cook 11 to 14 minutes, stirring every 2 minutes. Gradually add reserved water if sauce tightens before macaroni tender.
Remove from heat; rest 3 minutes. Divide among 6 bowls; scatter cheddar evenly over hot portions to soften.