Put the white beans in a colander and wash off with cold water. Then drain a little.
Peel and halve the onion (possibly quarter, depending on size) and cut into rings. Remove the stalks from the tomatoes and finely dice the tomatoes. Chop the basil.
Mix the beans, onion strips, diced tomatoes, basil and capers. Mix the vinegar, oil, salt and pepper in a bowl and add to the salad. Let it go a little.
A nice snack for two people or for four as a starter.