1 (2-pound) head cauliflower, green leaves discarded
1/4 cup plus 2 tablespoons extra-virgin olive oil
1 teaspoon salt
1 tablespoon fresh lemon juice, or to taste
1/4 teaspoon black pepper
2 cups loosely packed fresh flat-leaf parsley prigs
1 tablespoon drained small capers (packed in brine) (optional)
Put oven rack in middle position and preheat oven to 450°F. Lightly oil a 9-inch pie plate or square baking dish. Core cauliflower, leaving head intact, and put cauliflower in a pan. Drizzle 2 tablespoons olive oil over top of cauliflower and sprinkle with 1/2 teaspoon salt. Bake until tender, 1 to 1 1/4 hours.
Transfer to a serving dish.
Optional Topping: Whisk together lemon juice, capers, pepper, and remaining 1/2 teaspoon salt in a small bowl, then whisk in remaining 1/4 cup oil.