Preheat the oven to 350 degrees F (175 degrees C).

Place squash skin-sides down in a baking dish. Stab the outsides several times with a fork. Flip over and split butter evenly over the insides, coating the "bowls" with butter. Set aside.

Combine apple, potato, and kielbasa with onion and cranberries in a bowl. Pour in eggs and stir to combine. Heat a buttered frying pan over medium heat and pour in the egg mixture. Cook and stir until eggs are set, about 5 minutes. Scoop mixture into the squash bowls. Top with provolone cheese and cover with foil.

Bake in the preheated oven until squash is tender, about 45 minutes. Remove foil for the last 15 minutes for a crispy top.