Soak the dried bean kernels 12 hours beforehand. Cook the beans for about 2 hours (or 40 minutes if they are fresh). In the meantime, cut the onions as thinly as possible into rings and pick up the drained tuna a little. Arrange everything with the cold and well drained bean kernels in a bowl and season with good oil, balsamic vinegar, a little salt and freshly ground pepper.
Since this dish is only enjoyed cool, it is an absolute summer dish. However, the Florentines love it at any time of the year. We like to eat this salad as a summer dinner, with a little ciabatta or other bread.
Tip: Mix in strips of iceberg lettuce, romaine lettuce or sliced cucumber.