Be sure to use non-stick spray to coat the inside of your slow cooker. The tater tots will stick otherwise.
Brown your ground beef and onions together for that delicious flavor that only onions give. Drain grease, then stir in BBQ sauce.
Spread half the tater tots in a single layer on the bottom of your slow cooker. Spread all of your burger a.k.a. sloppy joe on top of the tater tots, all of the burger. The remaining tots on top.
Cook on low for 3 hours, then spread shredded cheddar cheese on top and cook for another 30 minutes or at least until the cheese has melted.