Watermelon Salad With Pickled Rind

Remove outer green rind from watermelon with a vegetable peeler; discard. Trim off ends. With watermelon standing upright, carefully cut white rind away from flesh. Place watermelon in a bowl or plate to avoid drips; cover and refrigerate until ready to use.

Chop white rind into 1/2-inch cubes. Stir vinegar, 1 cup water, sugar, kosher salt, mustard seeds, crushed red pepper, and black pepper in a saucepan. Bring to a boil over medium-high; boil for 1 minute. Remove from heat and add rind cubes. Let stand at room temperature, uncovered, for 1 hour. Refrigerate in liquid for 1 hour. (Pickled rind may be refrigerated in pickling liquid for up to 2 weeks.)

Meanwhile, process feta, yogurt, and whipping cream in a food processor until smooth, about 30 seconds. Add lemon juice; process until combined, about 15 seconds. Cover and refrigerate until ready to use (up to 3 days).

Quarter whole watermelon lengthwise and cut into slices. Spread whipped feta onto a large platter. Top with watermelon slices and arugula. Sprinkle with pistachios, desired amount of pickled rind, flaky sea salt, and black pepper. Drizzle with oil.