Heat oven to 400 ° F.
Toss the bread in a bowl with 1 1/2 tablespoons of the olive oil. Arrange in a single layer on a baking sheet. Bake until slightly golden and crispy, about 6 minutes. Transfer to a bowl and toss with the parsley and capers; set aside.
Meanwhile, heat the remaining oil and the garlic in a large skillet (preferably cast-iron) over medium-high heat. Season the steak with the salt and pepper and cook until browned, 2 minutes per side. Transfer the steak to a baking dish and roast to the desired doneness, 6 to 8 minutes for medium-rare. Let rest at least 4 minutes before slicing.
Add the cauliflower and 1/2 cup water to the skillet and cook, covered, until the cauliflower is tender and the water has evaporated, about 7 minutes. Divide the steak, cauliflower, and garlic among individual plates. Spoon the bread crumb mixture over the top.
Tip: Cooking the garlic in its peel flavors the cooking oil and leaves you with a tender, roasted clove inside. Eat it with the steak or spread it on toast for a quick, delicious hors d'oeuvre.