Slice the watermelon into bite-size cubes. Rinse and cut the tomatoes into wedges. Gently combine in a bowl or arrange on a platter.
Crumble the feta over the watermelon and tomato mixture, add the torn basil and drizzle with olive oil. Top with cashews and cucumbers and red onions if desired.
Season to taste with sea salt. Enjoy Watermelon Salad With Feta and Tomato!