Finely dice the onion, drain the corn and the tuna. Quarter the sheep`s cheese cubes from the glass again, do not pour off the oil. Alternatively, sheep`s cheese can also be taken out of the package and then cut into small cubes. Mix all ingredients in a bowl, season with salt and pepper to taste. Be careful with the salt, the sheep`s cheese already gives a lot of it. Pour some more oil from the sheep`s cheese glass over it and plenty of olive oil. If you take sheep`s cheese out of the package, you use more olive oil accordingly. The salad is our favorite barbecue salad, it goes incredibly fast and has been well received at all parties so far.