Preheat your oven to 425°F (220°C). Line a baking sheet with parchment paper for easy cleanup.
Remove the leaves from the cauliflower head and place it upside down on a cutting board. Using a sharp knife, carefully slice through the center of the cauliflower to create two halves. Then, cut each half into 1-inch thick steaks. You should get about 4-6 steaks, depending on the size of the cauliflower.
In a small bowl, whisk together the olive oil, lemon juice, lemon zest, minced garlic, thyme, oregano, red pepper flakes (if using), salt, and pepper until well combined.
Place the cauliflower steaks on the prepared baking sheet and brush both sides generously with the lemon herb mixture.
Roast in the preheated oven for 25-30 minutes, flipping the steaks halfway through, until they are golden brown and tender.
Remove the cauliflower steaks from the oven and let them cool slightly. Serve warm, garnished with fresh parsley.
Notes
For added flavor, allow the cauliflower to marinate in the lemon herb mixture for 30 minutes before roasting.