Preheat the oven to 400 degrees F. Trim the cauliflower by removing the green stalks on the bottom. Carefully remove the stem and the tough core, being careful to keep the head intact. Place it cut-side down in an 8x8 casserole dish or a cast iron pan.
In a small bowl, combine the olive oil, balsamic vinegar, Italian seasoning, garlic powder, salt, pepper, and lemon zest. Brush the mixture over top of the cauliflower and cover it with aluminum foil.
Bake for 30 minutes. Remove the foil and bake for an additional 15 minutes, until the cauliflower is soft when you pierce it with a knife. If you like a softer cauliflower, cook it for an additional 15 to 30 minutes, uncovered.
Carefully transfer the cooked cauliflower to a plate and sprinkle it with the chopped parsley. Serve immediately.