Melt butter in a large wok or skillet over high heat; saute onions and garlic until onions are almost transparent, about 5 minutes.

Combine curry powder, salt, turmeric, cayenne pepper, black pepper, ginger, and cinnamon in a bowl.

Stir ground beef into onion mixture and cook, breaking beef into small crumbles, until beef is cooked through and browned, 5 to 7 minutes. Add curry mixture to ground beef mixture and stir well.

Mix potatoes and tomatoes into ground beef mixture, reduce heat to medium, cover wok, and cook until potatoes are tender, about 20 minutes.