Watermelon salsa is perfect for a hot summer day. Start with fresh watermelon cut into cubes, then add a handful of thinly sliced mint and 1 finely chopped red onion. You can also add 2 chopped tomatoes, but you won't miss anything by leaving them out! Feel free to add some jalapeno or habanero chili pepper if you like it spicy; the combination of the sweet watermelon, the acidic tomatoes and the spicy chili peppers is pure heaven!