Slice the avocado into 3mm thick pieces and coat with lemon juice. Halve the cucumber vertically.

Cut the tuna into 2cm thick strips.

Mix sugar, salt, and vinegar in a bowl to make sushi vinegar. Pour over cooked rice and mix gently.

Mix eggs, mirin, and salt in a bowl. Heat salad oil in a pan and cook the egg mixture, rolling it into a tamagoyaki. Slice into halves.

Place a sheet of nori on a bamboo mat. Spread half of the sushi rice evenly. Cover with plastic wrap and flip over.

Layer tuna, cucumber, tamagoyaki, and lettuce on the nori. Roll tightly using the bamboo mat.

Lay avocado slices on plastic wrap. Place the roll on top and wrap tightly. Repeat for the second roll.