Combine tomatoes, toasted bread, basil, and onion in a large bowl.
To made vinaigrette, mix all ingredients (except the olive oil) in the blender.
While the blender is running on low, slowly pour olive oil into mix to emulsify.
Pour vinaigrette over salad mixture and mix.
Let the salad sit for at least 15-20 minutes before eating. (The bread should have time to soak up all the dressing.)