Shape the ground beef into 3 evenly sized patties, roughly matching the size of your bread slices. Season both sides generously with onion powder, garlic powder, salt, and pepper.

In a small bowl, combine mayonnaise, chopped bacon, ketchup, sugar, and relish. Mix until smooth and well blended. Set aside.

Heat a skillet over medium-high heat. Cook the patties until browned and cooked through, about 4–5 minutes per side. Remove from the skillet and set aside.

Clean the skillet and reduce the heat to medium. Butter one side of each slice of rye bread.

Place 3 slices of bread buttered-side down in the skillet. Top each with 2 slices of provolone cheese, one cooked patty, and 2 slices of cheddar cheese.

Spread a layer of the secret sauce on the unbuttered side of the remaining bread slices, then place them on top (sauce side down).

Toast the sandwiches until golden brown and the cheese has melted, about 3–4 minutes per side. Press lightly with a spatula for an even crust.

Slice in half, serve hot, and don’t forget to drizzle a bit more secret sauce on the side for dipping!