Low-Carb Chorizo Stuffed Spaghetti Squash

small or 1 medium spaghetti squash, seeds removed (800 g/ 1.76 lb)

ghee or lard (30 g/ 1.1 oz)

small white or brown onion, chopped (70 g/ 2.5 oz)

Mexican chorizo (1 lb)

chopped canned tomatoes (240 g/ 8.5 oz)

shredded cheddar cheese (113 g/ 4 oz)

salt (I like pink Himalayan salt)

freshly ground black pepper