Cut your watermelon in half, remove seeds if present, and cube the flesh into roughly 3/4-inch pieces. Place cubes in a colander lined with paper towels and refrigerate for at least 30 minutes. This step removes excess liquid that would otherwise dilute your dressing—I learned this after my first attempt turned into watermelon soup by hour two.

Dice your cucumber into 3/4-inch pieces matching the watermelon size. This uniformity isn't just pretty; it ensures every bite contains all the flavors rather than just vegetable texture. Toss cucumber into a separate bowl and set aside.

Thinly slice your red onion against the grain, aiming for delicate half-moons. If the onion tastes aggressively sharp when you sample a piece, soak slices in cold water for 5 minutes to mellow the bite. I do this when I'm serving people who don't usually enjoy raw onion—it's a small gesture that matters.

In a small bowl, whisk together olive oil, lemon juice, sea salt, and black pepper until the salt partially dissolves. Taste the dressing on a plain watermelon cube before proceeding—you want brightness without sourness overtaking the fruit's natural sweetness.

In a large serving bowl, combine your chilled watermelon cubes, diced cucumber, sliced red onion, and chopped mint. Pour the dressing over top and very gently fold everything together using a rubber spatula with a lifting motion rather than aggressive stirring. This prevents watermelon from breaking down.

Add crumbled feta cheese, parsley, and pomegranate seeds in the final minute before serving. The reason I wait until now is that feta needs minimal time to absorb liquid—when you add it too early, the salad becomes weepy and loses its elegance. Top with toasted pistachios right at service time so they stay crunchy.