Heat oil in a saucepan over medium-high heat. Add onion and saute until it begins to color, 2 to 3 minutes. Add garlic and cook for 1 minute more. Add soup, tomato, orzo and water. Bring to a boil. Reduce heat to low and simmer, covered, until the orzo is tender, about 10 minutes, stirring occasionally to prevent the orzo from sticking. Ladle into soup bowls and garnish with cheese and basil.