1: Trim, rinse and dry the tuna, then cut into thick portions. Salt and pepper on both sides.
2: Prepare the marinade by mixing 3 tablespoons olive oil, 3 tablespoons lemon juice, 2 tablespoons herbs of your choice, salt and pepper.
3: Put the tuna to marinate and leave for at least 30 minutes.
4: Heat a frying pan on medium heat without adding any fat. When hot, add the tuna. Cook for 2 minutes on the first side, then turn.
5: For perfectly cooked fish, stick an electronic thermometer into the centre of the tuna and watch the temperature. The fish will be perfectly cooked when it reaches 158°F (70°C). Turn off the heat immediately and leave the fish in the pan for a further 3 minutes to cook gently for a little longer.
6: Serve immediately with whatever accompaniment you choose. Here it is served with a red cabbage and walnut salad.
Remarks
It is not easy (maybe impossible even?) to give a precise cooking time for tuna, as this will depend on your hob and the thickness of the fish. This is why a thermometer is particularly useful in this recipe.