Cook the filling: In a large skillet over medium-high heat, add olive oil, diced peppers, and onions. Sauté for about 2 minutes. Add ground beef and cook until browned, breaking it up as it cooks. Drain excess grease if needed.
Season and simmer: Stir in garlic powder, chili powder, paprika, salt, pepper, ketchup, mustard, tomato paste, vinegar, and coconut aminos. Reduce heat and let the mixture simmer for 3–5 minutes, allowing the flavors to meld.
Assemble the casserole: Transfer the sloppy joe mixture into a 9x13-inch casserole dish. Top evenly with shredded cheddar cheese, then arrange tater tots over the top in a single layer.
Bake: Bake at 400°F for 25–30 minutes, until the tater tots are crispy and golden brown and the filling is bubbling around the edges.
Serve: Let cool slightly, then top with pickles or pickled onions if desired. Serve with a side salad or coleslaw for a complete meal.