Adapted from Marcella Hazan’s Essentials of Classic Italian Cooking
Combine in a saucepan:
2 pounds ripe tomatoes, frozen or fresh, or 2 cups canned, cut up into chunks with all their juice
5 tablespoons butter
1 medium onion, peeled and cut in half
Cook uncovered at a slow, steady simmer for 45 minutes. Taste and correct for salt. Pour through a colander or put through a food mill to remove the onion, skins, and seeds. Use it on pasta, with a sprinkle of parmesan. You can also freeze it after removing the onion, skins and seeds.