In a saucepan, warm the olive oil. Add the onions and garlic, sprinkle with the salt and saute on very low heat for 5 to 7 minutes, or until the onions are beginning to soften. Add the fennel, oregano, and basil and cook for another minute. Pour in the wine and bring to a boil.
Blend the tomatoes in a food processor until just pureed and add to the pan. Cover the sauce and simmer gently for about 20 minutes, stirring occasionally. Add salt and pepper to taste.