Preheat the oven (or air fryer) to 400˚F, and line a baking sheet with parchment paper.
Remove the leaves of the cauliflower using a sharp knife, and trim the bottom of the stem. Turn the cauliflower upside down, and slice the steaks through the central stem. For a large cauliflower, you may be able to cut 3 or 4 (½" - ¾" thick) steaks. For a smaller cauliflower you may only get 2 steaks.
Arrange the cauliflower steaks on the baking sheet and lightly drizzle with olive oil using no more than 2 tablespoons. Rub the oil over the cauliflower, flip them over and rub the oil on that surface too. (If using an air fryer, rub the oil over the cauliflower steak surfaces before placing them in the air fryer tray.) Lightly sprinkle the steaks with salt, pepper and Ancho pepper powder.
Roast for 20 minutes for ½" - ¾" steaks, or 30 minutes for 1" steaks, or until they reach the tenderness you prefer. Flip the steaks once during roasting. (Using an air fryer, cook for 12 - 15 minutes, depending on the thickness of the steaks. There's no need to flip the steaks over during cooking.)
While the steaks cook, pan roast the pumpkin seeds if you don't have them on hand.
While everything cooks, combine the remaining 1 tablespoon olive oil with the chopped parsley, and remaining salt and pepper to taste.
When the steaks are done, serve them over the Warm Lentil Salad (recipe below), and top them with the Lemon Tahini Dressing (recipe below), parsley-oil mixture, and roasted pumpkin seeds.