1. Peel the orange, taking care to remove the pith and eliminating the film from the whole segments. Do all this above a bowl so as to gather any drops of orange juice.

2. Put the orange juice, the oil, the sliced fennel and the finely chopped onion in a bowl and season with salt and pepper.

3. Arrange the tuna on a plate and garnish with the orange condiment. Serve immediately.

For a complete and light dish, try pairing the tuna and orange salad with 60g of spaghetti dressed with plenty of fresh basil-flavour tomato and 1 low-fat yogurt.