1/2 cup brown rice, chilled (You can also use quinoa or farro.)
Preheat cast-iron skillet to medium-high.
Salt and oil both sides of the steak. Use high heat oil for cooking.
Sear the steak. Cook to your desired doneness. For medium-rare, cook until the internal temperature is 115º. Let rest for 7 minutes.
In a medium-sized bowl, whisk together the yogurt, water, lemon juice, salt, and pepper. Stir in the apple, celery, grapes, and walnuts. Serve on a bed of fresh greens.