• Heat oven to 400°F. Line a rimmed baking sheet with parchment paper.

Prepare Cauliflower

• Trim and slice cauliflower into ¾-inch wide “steaks.” It’s ok if some florets come loose. Carefully place the cauliflower steaks on lined baking sheet. Drizzle with 4 tablespoons of olive oil and rub all sides of cauliflower. Generously season with salt; cauliflower requires heavy seasoning every step of the way. Roast cauliflower for about 30 minutes, flipping them over halfway through the roasting time, until both sides are deep golden brown.

Toast Breadcrumbs

• Heat 2 tablespoons olive oil in a pan over medium heat. If you use a pan that can also cook tomato sauce, you'll have one less pan to wash. Add breadcrumbs. Shake pan or stir until breadcrumbs are deep golden brown. Remove breadcrumbs from pan to a bowl right away. Residual heat from the pan can take the breadcrumbs from perfect to burnt pretty quickly, not that burnt is bad. That’s how I like my toast anyway.

Make Tomato Sauce

• While cauliflower is roasting, make tomato sauce. Heat 2 tablespoons olive oil in a saucepan over medium heat. (You can wipe out the pan you used for the breadcrumbs if the pan is large enough.) Add onions and garlic and cook until onions are translucent. Add finely chopped or crushed tomatoes, basil, and red pepper. Bring the tomato sauce to a boil, then reduce heat to simmer. Season with about ½ teaspoon salt, taste, and add more if needed. You can let the tomato sauce simmer until the cauliflower finishes roasting, or turn off the heat.

Assemble Cauliflower Parmesan

• Spread about 2 cups of tomato sauce in a baking dish. Place roasted cauliflower steaks on top. Cover the cauliflower with all the breadcrumbs, then grated parmesan cheese, then mozzarella cheese.
• Set the baking dish under the broiler in the oven until mozzarella melts and starts to bubble and brown.
• Garnish with chopped fresh basil and parsley. Serve with extra tomato sauce on the side.