If you are looking for a healthy, quick and successful main course, you ought to try marinated tuna fish. With its compact and flavourful flesh, tuna fish is rich in protein, minerals (iron, selenium, and phosphorus), vitamin A and precious polyunsaturated fatty acids, which play an important role in improving blood circulation. 

Tuna fish is very tasty and simple to cook. I would suggest that you try a recipe that my friend Lucia, who comes from Palermo, prepared for me last week. It is drawn from her family cookbook, that has been successfully handed down from generation to generation! And woe betide you if you buy the wrong type of tuna fish! She uses only the exquisite Mediterranean red tuna, because of its firm and fragrant flesh. But if you have trouble finding it, your trusted fish shop will certainly advise you on the right type of tuna you should choose for this recipe.

Ingredients (for 4 people)
1 kg (35.2 oz) of tuna fish cut in a single slice
1 onion
3 cups of extra-virgin olive oil
chopped up parsley
vinegar
salt
pepper
200 g (7.05 oz) of ground pistachios
a handful of fresh pistachios

First of all, prepare the marinade: chop up the onion and the parsley with an electric mixer or with a chopping knife and place the mixture in a large bowl. Pour the oil and the vinegar into the bowl and add the tuna fish. Let it marinate in the refrigerator for a few hours, after further seasoning it with salt and pepper. Spread the ground pistachios over a flat surface and place the tuna fish slice on top. Turn the slice in the ground pistachios to coat all sides. Preheat the oven to 180 °C (355 °F), in convection mode, put the tuna fish on the grill trivet, insert the probe into the thickest part of the fish, then set the core temperature between 40 °C (105 °F) and 55 °C (130 °F), according to the desired degree of cooking. As far as I am concerned, I prefer it rare, so I usually set the temperature low. Before serving, slice up the tuna fish and flavour it up with a drizzle of extra-virgin olive oil. Then decorate each slice with a few fresh pistachios. It is a quick recipe and it is always greatly appreciated!