I was looking for a beetroot and feta recipe and came across quite a few. Unfortunately all have ingredients that I did not possess. So I combined bits from a few of the recipes and made something so simple and yet it was yummy! To me anyway. And healthy!
Try to take chunks of the tuna onto your fork and then drop into the salad i.e. don't pour the oil all over the salad. You want some oil to remain in the tuna for a salad dressing. Whatever oil is left (and there should be some!) put drops here and there for additional dressing.