Dish with Diane — a series all about getting healthy and delicious foods right from world-class chefs themselves, brings you this special salad courtesy of beloved television chef, cookbook author, wife, mom and protégée of Julia Child, Sara Moulton. Loaded with pork tenderloin and watermelon, you won't need another salad all summer long!
Heat the grill to medium. Heat the oven to 400 F.
While the grill and oven are heating, in a blender combine half of the feta, the lemon juice, buttermilk and olive oil. Blend until smooth. Season with pepper, then stir in the remaining feta. Set aside.
Split each pita pocket into 2 rounds. Spray the rough sides of each round lightly with the cooking spray, then sprinkle lightly with salt. Cut each round into 8 triangles. On a rimmed baking sheet arrange the triangles in a single layer. Bake on the middle shelf of the oven until golden and crisp, about 8 minutes. Set aside to cool.
Spray the pork with the olive oil spray, then season it lightly with salt and pepper. Grill it directly over the heat, turning it a quarter turn at a time, until a thermometer inserted at the thickest part registers 140 F to 145 F for medium, about 6 minutes per side. Transfer the pork to a plate, cover it loosely with foil and let it rest for 10 minutes.
In a large bowl, combine the arugula, onion, mint, cilantro, watermelon and cucumber. Add the pork juices from the resting pork to the feta dressing, whisking to incorporate.
Place a mound of the salad on each of four plates. Slice the pork crosswise into rounds 1/2 inch thick and arrange a quarter of the slices on top of each mound of salad. Drizzle the dressing on top of the pork, then divide the pita croutons between the plates. Serve immediately.