Preheat the oven to 350 degrees F (175 degrees C). Grease a casserole dish.
Heat a skillet over medium heat. Add cabbage and cook until wilted, 5 to 7 minutes. Transfer to the prepared casserole dish.
Add hamburger and onion to the skillet and fry until brown and crumbly, 5 to 7 minutes. Drain and discard grease. Transfer mixture to the baking dish with the cabbage.
Pour spaghetti sauce on top of cabbage mixture in the baking dish. Top with mozzarella and Parmesan cheeses.
Bake in the preheated oven until brown and bubbly, about 30 minutes.
