Preheat the oven to 400 degrees Fahrenheit and line a large baking sheet with parchment paper.
Slice the cauliflower straight down the middle, then cut 1.5-inch thick steaks from the center halves, keeping the core intact.
Mix the olive oil, garlic powder, smoked paprika, onion powder, salt, and pepper in a small bowl.
Brush the spice mixture evenly over both sides of the cauliflower slices and any loose florets, then arrange them on the baking sheet.
Roast for 15 minutes, carefully flip the slices with a wide spatula, and bake for another 10 to 15 minutes until tender and crispy.
