Pulse bread, almonds, and garlic in a food processor until finely ground. Add red peppers, tomato, parsley, vinegar, and red pepper flakes. Purée until smooth; season with salt and black pepper.

Trim leaves from cauliflower heads. Place heads steam side down and cut, top to bottom, into 1-inch thick slices, or “steaks”. Place steaks on a sheet pan, brush both sides with oil, and season with salt and pepper.

Heat a large cast iron skillet over medium-high for 5 minutes. Add 2–3 steaks, place an additional cast iron skillet, or weighted pan, on top of steaks, and cook until charred, about 2–3 minutes. Flip steaks and cook another 2–3 minutes until charred. Transfer to a serving platter and repeat with remaining steaks. Garnish with parsley and serve with Romesco Sauce.