Cook sausage and onion in a soup pot until sausage is crumbled and onion tender. Add garlic and cook an additional minute.
Add the basil, salt, and pepper.
Next, add the diced tomatoes, tomato sauce, and water. Stir to combine.
Simmer for 5 minutes and add the orzo.
Continue simmering for about 10 minutes, or until orzo is tender.
Serve in bowls and top with parmesan cheese.