Preheat oven to 400Â°F.
Cut acorn squash in half lengthwise and scoop out seeds and fibers.
Place squash in a baking pan, cut side down, and add 1/2 inch of water.
Bake 20 minutes.
Meanwhile, saute ground beef in a skillet until browned.
Drain off excess fat.
Add butter, onion, apple, cabbage, and sunflower seeds and cook until vegetables are tender.
Add seasonings and mix well.
Turn squash halves cut side up and fill centers with cabbage mixture.
Return to baking pan and bake 30 minutes longer.