Add the tomatoes in boiling water for about 30 seconds. Then, lift them and put the boiled tomatoes in iced water for 20 seconds more. Right after, peel the tomatoes from the stem making sure to leave the flesh intact. Cut the tomatoes in half and with the help of a spoon, remove the seeds, and prepare the concasse cutting the flesh into small cubes. Cut finely the tuna, season with flakes of salt, pepper, olive oil and the peels of lime. Clean and cut finely the spring onions. Then, in a large covered pan, cook the onions with five tablespoons of olive oil , until they become very clear. In the meantime, cook the pasta, drain it al dente and the mix all with the spring onions and salt. Serve garnishing with slices of tuna, a little oil, basil leaves and tomato concasse.