To make the miso dressing, whisk all the ingredients together until well combined. Cover and refrigerate until ready to serve.
Cut watermelon into eight, 2cm thick wedges. Arrange the watermelon wedges on a large platter or board. Thickly slice the tomatoes into rounds and arrange over the watermelon.
Top with basil and sprinkle over the shichimi togarashi seasoning.
Stir the sesame seeds into the dressing and spoon over the watermelon. Serve with lime wedges.
TipTip: Shichimi Togarashi seasoning is a Japanese spice blend, if you can’t find it you can replace with dried chilli flakes. You will find it in the Japanese section of the supermarket.