4-5 medium tomatoes 
1/2 medium sized onion
1 scallion
1/4 cup of fresh cilantro
1 teaspoon of lemon or lime juice (mixed is OK)
1 teaspoon of vinegar
1/4 -1 jalapeno pepper (or a few dashes of Tabasco sauce)
1 clove of garlic (optional, but I use it)
salt and pepper to taste

Put all ingredients in blender and use pulse method to get the texture you  want. If I want a very coarse salsa I will blend only one tomato in the machine  and use a knife to cut the remaining tomatoes to the thickness I want.