Healthy Chili Cheese Burrito Squash Bowls

Name: Healthy Chili Cheese Burrito Squash Bowls
Ingredients: Optional: plain greek yogurt; 6 oz can of tomato paste; 1/4 cup chili powder*; 1/2 teaspoon salt; 2 teaspoon cornstarch; 2 teaspoon white distilled vinegar; 1/2 cup water; 1 1/3 cups shredded cheddar cheese (I like to use sharp cheddar, but whatever you've got will work!); 1 lb lean ground beef; 1/2 cup finely diced onion; 1 cup water; 1 medium-sized spaghetti squash (3 - 3 1/2 lbs), washed and pierced all over with a fork or knife (carefully!)