Ingredient:

• 1 medium-to-large shallot or ½ small red onion, sliced very thinly (about ½ cup)
• 3 tablespoons sherry vinegar or red wine vinegar
• ¼ teaspoon fine salt
• 3 pounds ripe seedless watermelon (about ½ small round watermelon or 4 cups cubed), cut into ¾″ cubes
• ½ cup crumbled feta (about 2 ounces)
• ⅓ cup roasted and salted pistachios, chopped
• ¼ cup extra-virgin olive oil
• Small handful of fresh mint and/or basil leaves, torn if large, for garnish
• Flaky salt or kosher salt, to taste