Frederic Patenaude, author of the best-selling e-book
"The Raw Secrets", has lots of awesome oil-free dressings. In one of his articles, he was sharing his basic method for making them:
"Start with tomatoes. Take 1-2 tomatoes, and put them in your blender, with the juice of half a lemon or some apple cider vinegar. Add in some sort of fatty food such as avocado. Then throw in some herbs of your choice (dill, chives, etc.), and some seasonings of your choice (if desired).
The result will be an incredibly tasty dressing you have spent about 2 minutes and half to prepare!"