Steps

• Start by cooking the rice: rinse the rice until the washing water is clear (yes, this can take a while...).
• In a saucepan, pour 500 mL of water and the rice, bring to a boil for 3 minutes then cook on low heat for 13 minutes (the water should be completely absorbed. If needed, you can add a little more water if it's absorbed before the allotted time).
• Stir the rice with a spatula to cool it down and add the sushi vinegar. Keep stirring, it should be completely cold.
• For the garnish, peel the mango and cucumber, and cut them into strips. Quarter the tomatoes, remove the pulp, and slice the flesh into strips.
• Place a sheet of nori on a mat. Wet your hands under water to dampen them, then take a handful of rice and spread it over 2/3 of the nori sheet. Lay strips of filling, alternating your ingredients at ¼ of the nori sheet.
• Then, roll everything using the mat, making sure to tighten well!
• And then cut into sections (about 5 for one nori sheet). Repeat the operation for the other sheets!