Wash and dry all of the vegetables very well—if you prefer to peel the tomatoes you can, although I usually leave the skin on.
Cut the tomatoes into 4 slices (leaving the core behind) and put into your blender.
Halve, core, and de-seed the pepper. Cut it into a few slices and add to the blender.
Peel the garlic and slice it in half. Remove the core (which often results in bitterness when not cooked).
Cut the onion into a few slices and add it to the blender too.
Peel the cucumber and cut it in half. Add half to the blender and save the other half for a topping.
Blend the vegetables at a high speed until it is completely pureed.
Add the salt and vinegar and, while blending on a slow speed, slowly add the olive oil.
Taste and adjust salt and vinegar. If the texture is too thick for your liking add some cold water.
Refrigerate and serve VERY cold! Add as many (or as few) toppings as you like.