Using a sharp knife, slice off the tops and bottoms of each of the tomatoes. Locate the fleshy dividing wall of one segment inside the tomato. Slice into the wall and open up the flesh to expose the seeds. Remove the seeds and their pulp by slicing through the tomato core. Set aside the seeds. Your aim is to keep the pulp of the seeds together to create tomato seed ?fillets? that are separate from the firmer tomato flesh. Repeat with each segment of the tomato.
Skewer one tomato seed fillet on each cube of watermelon. Arrange the skewers on a serving plate.
3. In a small bowl, mix the lemon juice with the oil, and vinegar and half of the lemon zest. Pour the dressing on the skewers. Sprinkle with sea salt, the remaining lemon zest and the mint. Serve immediately
Use a microplane for removing the zest from the lemon. If you want to save time, use cherry tomatoes instead of the tomato seeds.