Seed the tomatoes. I like to cut off the top slice and then gouge out the seeds over a bowl with my finger. Chop into quarters.
Cut the cucumber and peppers in half lengthwise and scoop out the seeds with a spoon; chop roughly.
Add 2 cups water to a blender and process some of the tomatoes, onion, cucumber, and peppers in batches. Empty the puree into a large bowl, reserving 2 cups of puree to process each new group of vegetables. Whisk in the vinegar, olive oil, and salt to taste. Chill in the refrigerator for at least 1 hour. Spoon into bowls and garnish with herbs, if using.