Season the steak with salt and pepper. Let it sit at room temperature for up to 30 minutes before cooking.
Heat the oil in a large skillet over medium-high heat until hot but not smoking. Sear the steak, turning once, until browned on both sides and cooked to your desired doneness. Figure 135°F (57°C) on an instant-read thermometer for medium-rare, 7 to 8 minutes total.
Meanwhile, bring a large pot of salted water to a boil, add the quinoa, reduce the heat, and simmer until the quinoa is tender, 10 to 12 minutes.
Drain the quinoa. Let it cool for 10 minutes.
When the steak is your desired doneness, let the steak rest on a cutting board for at least 10 minutes.
Thinly slice the rested steak on a diagonal.
Arrange the arugula, quinoa, carrots, and steak on individual plates. Sprinkle with the sunflower seeds and drizzle with the vinaigrette. (You may have some leftover vinaigrette. Stash it in the fridge.) Add some freshly cracked black pepper if desired. Serve immediately. Originally published May 28, 2016.