Rinse the rice and place in a pot with 250ml of water and a pinch of salt. Bring to the boil then bring to a simmer. Cook for 20 minutes then remove from the heat and leave to cool for a further 10 minutes.
While this is cooking, mix the sashimi grade tuna with the tamari, spring onion, rice vinegar, ½ the lime and sesame oil. Mix well.
Mix the pineapple with the jalapeño.
Plate everything together with the avocado and carrot and squeeze the rest of the lime over.