Put tofu, onion and remaining ingredients in blender. You may want to leave out the agave for now and see if you like the dressing without added sweetener. Add it at the end if you like.
If you don't have these exact herbs, other mild green herbs would also work in this recipe.
Blend all ingredients until smooth.
Recipe by Fit and Fed at http://fitandfed.net/2012/03/04/creamy-lemon-herb-salad-dressing-silken-tofu-based/