Prep the produce: Cube the watermelon, slice the tomatoes, and thinly slice the red onion. If using cucumber, slice it now.
Tear the basil and chop the mint just before assembling so they stay fragrant.
Make the dressing: In a small bowl, whisk together tamari, olive oil, and lime juice. Add honey if you want a softer, rounder finish. Taste and adjust—add another splash of lime for brightness or a touch more tamari for depth.
Assemble gently: In a large bowl, combine watermelon, tomatoes, cucumber, and red onion.
Pour the dressing over the top and toss very lightly with your hands or a wide spoon so the fruit doesn’t break down.
Add herbs and seasoning: Fold in basil and mint. Grind in black pepper. Taste.
If it needs more salt, add a pinch of flaky salt sparingly—remember the tamari is doing most of the salting.
Finish with texture: Sprinkle sesame seeds or crushed peanuts over the salad. Add cheese, if using, by gently nestling it throughout.
Serve right away: This salad shines when it’s fresh and cold. If you can, chill the ingredients before assembling for extra crispness.