Shape ground beef into 3 patties to match bread size. Season with onion powder, garlic powder, salt, and pepper.
Sear patties in a skillet over medium-high heat for 4–5 minutes per side until fully cooked. Set aside.
Mix mayo, bacon, ketchup, sugar, and relish in a small bowl until smooth.
Butter one side of each bread slice. In a clean skillet, place 3 slices buttered-side down. Layer with provolone, patty, cheddar, and top slice with sauce facing in.
Cook each sandwich over medium heat until golden and cheese melts, about 2–3 minutes per side.
Slice and serve hot while the cheese is still gooey.