Halve squash lengthwise and remove seeds.
Bake cut side down in shallow baking pan at 350° for 35 to 40 minutes.
Turn cut side up; sprinkle with salt.
Fill halves with onions and walnuts.
Combine butter, dark corn syrup, 1/4 teaspoon salt, and ground cinnamon.
Spoon over filling.
Continue baking 15 to 20 minutes or till squash is tender, brushing occasionally with syrup to glaze.