Suggested seasoning: extra virgin olive oil, salt, lemon zest. 

Instruction: in a small bowl gather fresh, rinsed and dried basilikum, garlic cloves, some walnuts and pines; mix it all with a blender and add extra virgin olive oil until a soft pesto cream is obtained. Grill the yellowfin tuna steak. Separately cut the tomatoes into cubes and chop the parsley; merge everything with the seasoning at the serving dish.