1 pound ground beef
1/3 cup diced sweet onion
2/3 cup ketchup
2 Tablespoons yellow mustard
2 Tablespoons dill pickle relish
2 Tablespoons butter
2 Tablespoons all-purpose flour
1 1/2 cups milk
1/4 teaspoon kosher salt
1/4 teaspoon ground black pepper
2 cups Cheddar Shredded Cheese, divided for insude and on top
32 ounce bag Tater Tots