2. Seed and dice the jalapeño peppers.
3. Bring a medium-sized pot of water to a boil. Core the tomatoes and drop in the water a few at a time, for about 10 seconds, just long enough to loosen the skins. Scoop the tomatoes out of the water.
4. Rinse the tomatoes under cold water to cool them, then slip off their skins. Place a mesh strainer over a bowl. Cut the tomatoes in half crosswise and squeeze out the juice and seeds over the strainer. Save the juice to add to the soup and discard the seeds.
5. Puree half of the tomatoes in a blender or food processor and coarsely chop the rest. Combine all of the tomatoes, onion, cucumber, jalapeños and basil in a large bowl. Season with salt, pepper, vinegar and lime juice. Refrigerate and let sit for at least 1 hour to allow the flavors to develop. Serve chilled.