Fill a large saucepan with 1 inch of water and fit it with a steamer basket. Bring the water to a boil.
Place the cauliflower in the basket, cover, and steam until very tender, 8 to 10 minutes. Drain.
Meanwhile, heat 1 teaspoon oil in a large skillet over medium-high heat.
Season the steaks with ½ teaspoon each salt and pepper. Cook 4 to 6 minutes per side for medium-rare. Let rest before slicing.
While the steaks cook, transfer the drained cauliflower to a food processor. Add 2 tablespoons oil and ¼ teaspoon each salt and pepper. Puree until smooth.
In a bowl, combine the parsley, olives, shallot, vinegar, remaining oil, and ¼ teaspoon each salt and pepper. Serve with steak and cauliflower.