In 12-inch skillet, cook ground beef over medium-high heat, stirring frequently, until thoroughly cooked; drain.
Stir in uncooked pasta, chili powder, water and tomatoes. Heat to boiling, stirring frequently. Reduce heat to medium-low; cover and simmer 10 to 12 minutes, stirring occasionally, until pasta is tender.
Remove from heat; let stand uncovered 5 minutes. Stir in cheese until melted. Sprinkle with additional chili powder.