Tuna cut into very small cubes;

Chop the onion and cilantro in a blender to fine crumb;

Add chopped vegetables, lime juice, sesame oil and soy sauce to tuna.

Spread the resulting mass on a plate in a special salad form (if there is no form, you can use a small saucer with low sides), tamp with a spoon.

Remove the form (or turn the saucer on a plate for serving).

From above decorate sesame seeds.