Arrange potato in a steamer basket over boiling water. Cover and steam 10 minutes or until tender. Remove from heat.
Coat a large nonstick skillet with cooking spray; add oil. Place over medium-high heat until hot. Add onion; sauté 3 minutes or until tender. Add potato, chili powder, and salt. Cook 5 minutes or until potato is lightly browned, stirring often. Sprinkle cheese over potato. Cover, remove from heat, and let stand 1 minute or until cheese melts.