Brown beef in a skillet for 8 to 10 minutes, breaking it into small crumbles, until it reaches 160°F. Drain fat, stir in chili powder, cumin, beef salt, garlic powder and water and cook for 1 minute. Spread in a shallow dish and refrigerate promptly while preparing the rest.
Boil macaroni in water with the tablespoon salt until fully tender. Drain, rinse under cool water and drain thoroughly.
Mix sour cream, mayonnaise, salsa and lime juice in a large bowl. Add pasta, cooled beef, tomatoes and cheddar and fold until coated.
Fold in romaine just before serving. If making ahead, refrigerate the dressed pasta mixture and keep the lettuce separate until needed.
Serve cold or cool and refrigerate leftovers within 2 hours.