Place racks in the center and upper third of your oven. Preheat the oven to 425°F. Line a large baking sheet with parchment paper.
Place the caulilfower on a cutting board and sliced off the base so that it forms a flat surface. Cut away the thick green stems. Stand it up on its cut end, with the florets-side up. Working from top to bottom, slice the head into 1-inch thick "steaks," starting from the center and working your way out. Some of the slices may break apart and florets on the sides will fall away. Arrange all of the cauliflower, both steaks and florets, in a single layer on the prepared baking sheet.
In a small bowl, stir together the oil, Italian seasoning, garlic powder, salt, and pepper. Brush over both sides of the cauliflower steaks and florets. Turn any loose florets so that their flat, cut sides are facing down and touching the surface of the pan.
Bake the cauliflower of the center rack for 20 minutes. Remove from the oven and with a think, flexible spatula, gently turn the steaks and florets over. Sprinkle the Parmesan over the top. Return the pan to the oven and continue baking until the Parmesan turns golden and the caulfower is tender and caramelized at the edges, 18-20 additional minutes. Remove the pan from the oven and turn the oven to broil.
While the caulfower bakes, prepare any noodles you'd like to serve with the cauliflower. If youd like additional sauce to serve on the side with the noodles, warm it in a small saucepan over medium heat (reserve 1 cup sauce for baking the cauliflower).
Once the cauliflower has baked, spoon 1 cup sauce over the top. Sprinkle with the mozzarella. Return the cauliflower to the oven, placing the pan on the upper rack. Broil until the cheese is melted and turning golden, 1 to 3 minutes. Do not walk away from the oven, to ensure the cauliflower does not burn. Sprinkle with the basil. Enjoy immediately, with noodles and warmed sauce if desired.
Make-Ahead: The cauliflower steaks and florets can be cut and stored in the refrigerator up to 1 day in advance.Storage: Refrigerate leftovers in an airtight container for up to 3 days. If serving with pasta or vegetable noodles, store the noodles in a separate container. Rewarm the cauliflower in a 400°F oven for 8-10 minutes, until heated through.