Step 1

Grease a 20cm square cake pan. Line base and sides with baking paper, allowing a 3cm overhang on all sides. Place rice and 1 1/2 cups cold water in a saucepan. Cook, following absorption directions on packet, until tender. Stir in vinegar. Spread rice over a large baking tray.

Step 2

Meanwhile, combine salmon, mayonnaise and onion in a bowl. Trim nori sheets to fit prepared pan. Place 1 sheet, shiny side-down, in base of pan. Spoon half the rice over nori, using the back of a wet spoon to spread evenly (rice will be quite sticky). Place avocado, in a single layer, over rice. Top with salmon mixture. Place cucumber, in a single layer, over salmon. Spoon remaining rice over cucumber, using the back of a wet spoon to spread evenly. Place remaining sheet, shiny side-up, over rice. Press firmly to secure. Refrigerate, covered, for 2 hours or until set.

Step 3

Carefully remove slice from pan. Cut into 16 squares. Serve.