Flank Steak with Cauliflower Purée

Fill a large saucepan with 1 in. of water and fit with a steamer basket. Bring the water to a boil. Place the cauliflower in the basket, cover and steam until tender, 10 to 12 minutes. Drain. Meanwhile, heat 1 Tbsp oil in a large skillet over medium heat. Season the flank steak with 1/2 tsp each salt and pepper, and cook to desired doneness, 5 to 6 minutes per side for medium-rare. Let rest for at least 5 minutes before slicing. Transfer the cauliflower to a food processor, add 1 Tbsp oil and 1/4 tsp each salt and pepper and purée until smooth. In a small bowl, combine the parsley, vinegar, capers, shallot and remaining 2 Tbsp oil. Serve with the steak and cauliflower.