While the pasta is cooking in salted boiling water, prepare the salad by adding the cherry tomatoes, arugula, bocconcini, and basil leaves to a large salad bowl.
Heat the olive oil in a hot skillet and pan-sear the tuna, leaving the middle of the filet as pink as possible. Let the tuna cool before cutting it into slices.
Once the pasta is al dente, drain all the water and rinse the farfalle with cold water. This will help stop the cooking process and it will keep the pasta firm.
Mix the cooked pasta together with the other ingredients, and season with salt and a drizzle of olive oil.