Cooked rice cooled and mixed with drained tuna, corn, cherry tomatoes and onion, with parmesan over the top. Thirty minutes, four servings, and it is a good use for rice left over from another meal.
Cool the rice completely before anything else goes in. Warm rice heats the tuna, softens the tomato and makes the whole bowl weep water, and there is no recovering from it. Spread it out on a tray if you are in a hurry: a mound of rice holds its heat for a surprisingly long time. Drain the tuna and the corn properly for the same reason. Tinned liquid is the other thing that turns a rice salad into a wet one. This is also what to do with rice left over from a previous meal, which is already cold and already separated. Add the parmesan at the table rather than in the bowl, which is what the sixth step is getting at: mixed in early it clumps against the damp rice.