Peel the potatoes, cut into wedges and cook in salted water for about 20 minutes. Peel the asparagus, cook in salted water and drain well. Squeeze the limes and grate the peel finely. Store juice and peel separately.
Mix a marinade from olive oil, lime juice, salt, pepper and marjoram and marinate the asparagus in it. Fry the potatoes with rosemary in olive oil until crispy, season with salt and pepper.
Crush the pepper and mix it with the grated lime zest. Roll the tuna steaks in it and fry them in a pan until crispy. Just before the end of the roast, add a little salt on both sides.
Serve the fish with the asparagus and potatoes and decorate with a sprig of rosemary. Possibly serve hollandaise sauce with it.