Heat oven to 400 degrees. Trim bottom of cauliflower and remove all leaves and hard stem but without breaking apart the cauliflower. Rinse and pat dry. Generously drizzle olive oil on top. Add salt and pepper. Using your hands, spread oil, salt and pepper all around the cauliflower. Put in oven safe pan and cover with foil, without any gaps.
Bake for 40-50 minutes, depending on the size of your cauliflower. Check with a knife. If it slides in easily, then it’s cooked. Remove foil and allow to roast an extra 5-10 minutes until golden brown. Melt 3 Tbsp. butter. Mix in parsley. Brush on butter mixture while cauliflower is still hot.