Cut tuna fillet into narrow slices and place in a shallow work bowl. Slit open the chilies, remove the seeds and dice very finely. Stir through the finely grated lime zest and 2-3 tbsp lime juice, sesame oil, oil, soy sauce and pepper.
Drizzle half of the sauce over the tuna and marinate the fish in it for 15-20 minutes. Clean, rinse and spin dry arugula. Rinse and dry cherry tomatoes and cut into quarters.
Toast the sesame seeds in a dry frying pan.
Toss the arugula with the remaining dressing and arrange on a large platter with the sesame seeds, tomato quarters, alfalfa sprouts and the tuna slices and bring to the table on the spot.
Drizzle with lime.