Rinse and pat-dry the tuna and cut the fillet into small steaks.
Prepare the marinade. Mince rosemary leaves, fennel and garlic, and mix with olive oil until blended. Sprinkle one tablespoon of Vegeta blend on tuna steaks, put them into the prepared marinade and leave for about 10 minutes to marinate.
Remove with slotted spoon and sear the steaks in a hot skillet on both sides (tuna should remain pink in the centre). Add some of the remaining marinade.
Arrange a bed of rocket leaves and corn salad on serving plates. Add some diced blood orange and olives, and drizzle with olive oil and vinegar. Arrange the fried tuna steaks on top. Drizzle with a little marinade and serve.
Perfectly cooked tuna steaks should be well seared on the outside, and pink and soft inside. Tuna dries out easily so make sure to keep it juicy and silken by adding tuna steaks to the moderately hot but not too hot olive oil and by flipping the steak only when the bottom side is seared.