In a 10- to 12-inch frying pan over medium-high heat, stir ground beef, cumin, and pepper until beef is crumbled and browned, 10 to 12 minutes.
Meanwhile, peel potato. Coarsely shred, immersing shreds in cool water as you go; drain well.
Add potato to beef and stir occasionally until potato is tender to bite and beef is very well browned, 10 to 12 minutes longer. Add salt to taste.