Lay squash on its side and cut off 1/4 of it to make a lid. Remove seed and strings. Melt butter in skillet, add onion and saute until soft about 5 minutes.
Add apples, cinnamon, raisins and sunflower kernels. Stir and toss until well mixed. Cook about 5 minutes. Scoop apple mixture into squash and replace lid. Place on baking sheet and bake at 350 degrees until tender, about 1 1/2 hours. Garnish. Serves 8.