Cook the macaroni in simmering water according to package directions until al dente.
Drain well and return it to the cooking pot.
While the pasta cooks, heat the oil in a separate saucepan over medium heat.
Add the finely chopped onion and cook until translucent.
Stir in the diced tomatoes and nutritional yeast and cook for another minute.
Add the Gee Whiz Spread or non-dairy cheese, mixing well until it's melted and the sauce is smooth and heated through.
Pour the hot cheese sauce over the cooked pasta in the pot.
Stir until the macaroni is thoroughly coated.
Season to taste with salt and pepper before serving immediately.