In a saucepan, boil tomatoes and jalapeno pepper in water for about 8 minutes. Drain the water and allow the tomatoes and jalapeno peppers to cool.
Remove the skins from the tomatoes and put them in the blender or food processor with all of the remaining items (except the onions). Blend for about a minute or two until the mixture is smooth.
Now add yellow onions and just pulse blender or food processor to mix up the onions with the rest of the ingredients (if you prefer your salsa texture to be chunky, then only blend the tomatoes for 30 second).