This is a really wonderful and light appetizer that could easily be converted into a nice summer lunch as well. If I'd do this as a lunch, i would probably serve a bit of toasted bread and a salad with it. Important is, that you use really good quality tuna, preferrably sushi quality.
Appetizer for 2 people:
1 nice and superfresh tuna steak, finely cut into small pieces
freshly ground salt and pepper
1/2 yellow onion, finely chopped
1 egg yolk
2 tablespoons olive oil
1/2 cup non-fat yoghurt
1 spring onion, finely chopped
2 spring onions for decoration
slice of lemon
Mix tuna, onion, egg yolk and freshly ground salt and pepper in a bowl. By hand, form a patty with the tuna mix. Press it enough to make it as firm as possible.
For the sauce, combine yoghurt, finely chopped spring onions and salt and pepper in a small bowl. Cut the 2 remaining spring onions into about 10 cm pieces.
Heat the olive oil over high heat in a small non-stick skillet. Once the oil starts smoking a bit (when it's really hot), carefully place the tuna patty into the skillet. Grill it about 1 minute on one side without touching it, then flip it and give it another minute. Arrange the patty, the yoghurt sauce, the lemon slice and the spring onions nicely on a plate. Before eating, squeeze the lemon over the patty and enjoy!