I think the best way to prepare red tuna is quick-seared, so it is raw/red in the center. If it is overcooked (well-done), it is in my book, inedible.

It is important not to use a thin piece of tuna. Better ask your fishmonger to cut you a thick piece, about 3-5 cm.

This recipe takes under 10 minutes to make, but it is a good idea to take the fish out of the fridge well in advance, so the meat reaches a slightly higher temperature before cooking. This reduces the likelihood of the meat "boiling" in the pan.

Start by heating a thick-bottomed pan, meanwhile, brush the fish with a mixture of lemon juice/oil/salt/pepper.

Put some oil on the pan and sear your tuna for 1 minute.

Flip it and sear for another minute on the other side.

Stand the steak on its edge and sear for 20 seconds on each side to get a seared crust all the way around.

Slice the steak thinly and serve immediately.