I make tomato sauce from Roma tomatoes that I grow in my garden. I add celery, carrots, peppers (hot and not), onions, and parsley that I also grow in my garden. I don't peel the tomatoes, which I understand can make the sauce bitter. I blend everything together in a blender and then cook it until it's quite thick. What can I add to this sauce to remove the bitterness? I don't want to peel the tomatoes. I'd like to find another way to remove the bitterness.