Heat oven to 475 degrees F. Place the beef on a large rimmed baking sheet. Rub with 1 tablespoon olive oil, salt, and pepper. Bake at 475 degrees F for 12 minutes.
Meanwhile, toss 2 tablespoons oil with cauliflower and shallots; season with additional salt and pepper. Quickly scatter vegetables around beef in the pan and continue to bake, stirring vegetables once, 18 more minutes (for medium-rare) or until meat reached desired degree of doneness.
Remove beef from pan and cover with foil; let stand 15 minutes. Whisk together remaining 3 tablespoons olive oil, lemon juice, and mustard; season with salt and pepper to taste. Stir kale into hot pan with vegetables. Drizzle with olive oil mixture and sprinkle with pomegranate seeds. Slice beef and serve with cauliflower pomegranate salad.