Cut the stem of the half cayenne pepper, remove the seeds and finely chop the flesh. Halve the cherry tomatoes.
Mix the drained tuna with the cayenne pepper and season with salt.
Squeeze the lime. Make a cut in the avocados around the stone. Twist the two halves apart. Spoon out the stone. Scoop out the flesh with a spoon and cut it into small cubes of about 1 cm. Mix the avocado cubes with 2/3 of the lime juice.
Mix the mayonnaise with the wasabi and the two types of sesame seeds. Season with the rest of the lime juice.
Rinse the serving ring with water. Do not dry it! Place in the centre of a plate. Fill the ring with a layer of avocado. Press the top down a little. Put a layer of tuna on it, then press again. Finish with a layer of avocado. Carefully remove the ring and make a total of 8 towers.
Spread the wasabi mayonnaise over the top, and garnish with an edible pansy, cherry tomatoes and extra sesame seeds.
