Preheat your oven to 425°F (218°C) and prepare a baking sheet with parchment paper.

Slice the cauliflower heads into approximately 3/4 inch thick pieces and arrange them on the baking sheet. You'll get 2-3 substantial slices from each head; any smaller pieces can be used for another dish or roasted along with the steaks.

Combine olive oil, salt, black pepper, smoked paprika, and onion powder in a small bowl. Brush this mixture evenly over both sides of the cauliflower slices.

For the oven method: Bake the cauliflower steaks for 10 minutes. Turn them over and bake for an additional 10-15 minutes until they are tender and golden brown.

For the grill method: Heat your grill to medium heat. Place the cauliflower steaks on the grill, cover, and cook for 5 minutes. Flip the steaks, cover again, and grill for an additional 4-5 minutes until they are tender and have a nice char.