Heat the grill to high. Prick the potatoes with a fork, then microwave on high for 10 mins. Rub with the olive oil and season with salt. Transfer to a baking sheet and grill for 5 mins or until the skin is crisp and blistered.

Tip the tuna into a mixing bowl and combine with the pesto, yogurt, lemon zest, most of the herbs and the roasted pepper, then gently stir in the cucumber, remaining herbs, feta and lemon juice. Season.

Split the sweet potatoes open and fill with the tuna mixture, top with extra dill and serve with salad, if you like.