I have a recipe for homemade tomato sauce that I use all the time. Here it is:

1 can (6oz) tomato paste
1 1/2 c. water
5 ripe tomatoes, peeled and cut
1/4 c. olive oil
2 garlic cloves
1/4 c. butter
1/4 tsp. dried basil
1/4 tsp. crushed red pepper
salt and pepper to taste

Blend tomato paste with water. Add tomatoes, oil, and garlic. Simmer until reduced to 1/3 of its original amount. Put through food mill. Add remaining ingredients, season to taste with salt and pepper, and continue simmering until sauce is reduced to half its original volume.