Slice the tuna loin into thin slices 3mm thick.
Prepare the sauce vierge: remove the skins from the cherry tomatoes by immersing in boiling water for 10 seconds and then placing them straight into iced water. Remove the skins with your fingers and the cut the tomatoes in half. Season with salt to draw out the juices. Finely dice the shallots and the garlic and mix with the tomatoes. Leave this for one hour at room temperature. To finish the sauce, shred the basil and add along with the olive oil and black olives. Check the seasoning.
To prepare the fennel and kohlrabi: cut the fennel in half, remove the tough core and slice finely on a mandolin. Peel the kohlrabi and finely slice on a julienne mandolin. Wilt the fennel and kohlrabi by lightly seasoning with salt. Place in a colander and allow the water to drain off. Pick and chop the parsley. Dress the slaw with olive oil, parsley and lemon juice.
Heat a griddle until hot. Season the tuna with Maldon sea salt and a drizzle of olive oil. Cook on the griddle for 1 minute on each side.
To assemble the dish: place the tuna on top of a bed of the slaw and drizzle the sauce vierge over the dish.
«The tune will only take seconds to cook on a very hot griddle. It should still be rare when served.»