Lay diced watermelon on a platter, and top with red onion and halved cherry tomatoes.
Top with the mozzarella and fresh basil.
Drizzle over the balsamic glaze and serve.
Notes
For an ultra-easy salad, you can use packaged cut watermelon.
I highly recommend using seedless watermelon. If you use watermelon with seeds, make sure to pick out any of the large black seeds, as they're not very pleasant to eat.
Use a high moisture mozzarella like mozzarella pearls or a torn up mozzarella ball. Low-moisture mozzarella, usually sold in blocks, is too hard and has a saltier, cheesier flavor.
I don't recommend making this salad ahead or storing it for later. The onion flavor tends to soak into everything over time, overpowering the gentler flavors. Make it fresh for the best experience!
Balsamic glaze isn't the same as balsamic dressing! The glaze is sweeter and stickier, making it ideal for this salad that already has plenty of juicy ingredients.
Cut the onion as thinly as possible! Thick slices are unpleasant in this salad; you want the slices very thin, as thin as you can cut. Use your sharpest knife.