Preheat oven to 375F
In a large pan Cook the onion til translucent. Stir in beef and cook til browned.
Add salsa and bring to a simmer. Stir in soup and bring to a simmer.
In a large 13x9 baking dish lay out a layer of tater tots. Cover with half the cheese. Add beef mix and spread evenly. Add remaining tater tots and cover with remaining cheese.
Bake at 375F for 30 minutes