1. Poke holes in the squash with a fork, and microwave entire squash for 5 minutes. Cut in half, remove the seeds, place in a covered dish with 1/4 inch of water and microwave an additional 5 minutes.
2. In a skillet over medium heat, add the butter, onions, red pepper and cook until the onions are slightly brown.
3. Using a fork, scrape the insides of the squash and transfer to a bowl. Combine the squash, onions, sour cream, and half of the cheddar cheese and mix well.
4. Transfer to a baking dish and top with remaining cheese. Bake at 375o for 15-20 minutes.