Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper and set aside.
Place one whole head of cauliflower stem side down on a cutting board. Cut it in half from top to bottom. Cut a 1-inch slice from the center of one of the halves. If the cauliflower is large enough, you can try cutting another 1-inch slice from whatever remains from that same half. Repeat with the other half.
Carefully trim off excess leaves. You can trim the stem a bit, but make sure you don't cut too close to where the florets are attached or they will fall apart.
If you only got 2 good slices from the first cauliflower, repeat the process with a second one, so you have 4 cauliflower steaks.
Place them flat on the prepared baking sheet in one even layer with space in between each one. Brush a little oil all over each slice.
Mix together the salt, Italian seasoning, paprika, garlic powder, and pepper. Sprinkle over each slice.
Gently turn each cauliflower slice over and repeat with the oil and spice mixture on the second side.
Roast for 15 minutes. Gently flip each "steak" over. They will become more delicate as they cook, so a wide spatula works best. Roast another 10 to 15 minutes until the cauliflower is tender and the edges are browned and caramelized.
Sprinkle some fresh chopped parsley over the top, if desired. Serve hot.