Preheat oven to 400.
Cook and ground the chorizo meat with the chopped onion. (About 1/2-3/4 lb ground sausage would be a good replacement for the chorizo.)
While chorizo is cooking, prepare the squash by slicing off the top/stem and the little tail. Cut across the equator and remove the seeds. Place "bowl-side" up in a glass baking dish with 1/4 inch of water. (The water acts as an additional steaming agent for the squash as they roast in the oven.)
Once chorizo has cooked, place in a bowl and toss with the chopped apples and cooked rice. Season with a little salt and pepper. Fill the squash bowls with chorizo-apple mixture.
Roast in the preheated oven for 45-50 minutes, or until flesh on the squash is tender.
Let cool slightly before serving. If desired top with Parmesan cheese before serving.
Serve Chorizo-Apple Stuffed Acorn Squash, as is or with side of bread.