For the cured tuna

• Combine water, salt and sugar.Stir until salt and sugar are completely dissolved. Slice tuna into 100 gr. Place tuna in brine and let stand for 30 min. Stir the fish every 10 min so that all sides of the flesh are brined equally. Remove fish from brine and on a paper towel to dry. Place the tuna with the olive oil, lemon zest, rosemary in a dip sauce pan and cook at 45c for 30 min. Remove the tuna from the oil and place in a dip bowl. Cool tuna in bain marie with cold water and ice cubes.

For the lemon dressing

• In a small mixer, pour all the ingredients and beat well until the mixture is homogenized.

For the salad

• Wash and scrub any grit from the potatoes. Cut them into half. Transfer the potatoes to a large saucepan. Cover the potatoes with cold water. Bring to a boil. Adjust the heat to keep the water at gentle simmer Cook until potatoes are tender all the way through when pierced with a knife. Drain the potatoes. In a dip bowl combine the potatoes with the capers, radishes, caper leaves, 1 tbsp of the lemon dressing, salt and pepper and mix gently

How to serve

• Place the potato salad in a bowl plate, on the top place small pieces of the cured tuna and the salad leaves. Toss the salad  with the rest of the lemon dressing.