Make the bacon: Line a rimmed cooking sheet with foil. Put the bacon in a single layer on the sheet. Throw in the oven for 10 minutes, then rotate the pan and leave in there for 5–15 minutes more (depends on thickness) until the bacon is well-done and dark. Place the bacon on a paper-towel lined plate. Reserve some of the grease from the sheet for the casserole dish.
While that’s going on, in a large skillet on medium heat with some oil (or some of the bacon grease!), sauté the onions and a big pinch of salt until translucent (7-ish minutes).
Add the ground beef and another pinch of salt and cook until browned. If it’s a wet mess now, drain it.
Mix in ketchup, mustard, and pickle bits. Crumble the bacon strips and mix that in too. Season to taste with salt and pepper.
Grease a 9x9in casserole dish with some of the bacon grease. Or Pam. Whatever. Put the meat mixture in there, then top with the tater tots in a single layer.
Place in oven. Reduce temp to 400℉. Cook for 35 mins or until the tots are browned.
Sprinkle a little salt on the tots. Top with american cheese slices and put back in the oven for another 1–2 minutes until melted.