Wash, clean and dice the peppers and cucumber. Mix with the corn, beans and drained tuna. Incidentally, capers or spring onions can also be served as desired.
Now make the dressing from the remaining ingredients. Most of the time I make the sauces free snout; It should be roughly: 1 tablespoon mustard, 6 tablespoons vinegar, 1 teaspoon sugar, stir this and then fill up with oil. Pour the dressing over the salad and let it steep for a while.