(approx 15 units) ripe plum tomatoes • medium-size (1/3 pound) red onion • medium-size (1/2 pound) cucumber • red or green (1/3 pound) bell bepper • garlic, peeled and chopped • kosher salt • (about 2 slices) soft white bread, crust removed • olive oil, more for serving • sherry vinegar, more for serving • finely chopped chives • Ground black pepper