Tomato Gravy

2 cups chopped tomatoes
1/2 cup chopped onion
2 cups water
3 tablespoons dissolved cornstarch
1 tablespoon oi
1/4 cup grated cheese
1 teaspoon salt
1 teaspoon vetsin

Saute onions in oil. Add the tomatoes well. Add the water and let boil. Season with salt and vetsin. Thicken with cornstarch.