Preheat your oven to 450º F. Cut off the leaves from the cauliflower's base with a sharp knife. Slice the cauliflower in half, then cut 2 steaks, each about 1 inch thick, from each half.

In a small bowl, combine the olive oil, sea salt, garlic powder, onion powder, smoked paprika, and chili powder.

Place the cauliflower steaks on a baking sheet. Brush the top sides with half of the olive oil mixture. Put the baking sheet in the preheated oven.

Roast the cauliflower steaks for 15 minutes. Remove the baking sheet from the oven and carefully flip the steaks over. Brush the tops with the remaining olive oil mixture.

Return the baking sheet to the oven and roast for another 15 minutes, or until the steaks are golden brown and tender.

Take the baking sheet out of the oven. Move the cauliflower steaks to serving plates, garnish with parsley if you like, and serve warm.