- 2 bunches broccoli (about 3 pounds), stalks trimmed, tops broken into 2- to 3-inch florets
- 1/4 cup (1/2 stick) unsalted butter, cut into very thin slices plus more for dish
- 1/4 teaspoon dried crushed red pepper
- Coarse sea salt (preferably gray crystals)
- Freshly ground black pepper
- 2/3 cup freshly grated Pecorino Romano cheese (1 1/2 to 2 ounces)
- Cook broccoli in boiling salted water until crisp-tender but still bright green, about 5 minutes. Drain and cool. Cut florets lengthwise into 1/4-inch-thick slices. Coat large oval gratin or 13x9x2-inch glass baking dish with butter. Arrange broccoli slices, overlapping snugly, in rows in dish. Sprinkle with crushed red pepper, salt, and black pepper. Dot with 1/4 cup butter, then sprinkle with cheese. DO AHEAD: Can be made 8 hours ahead. Cover and chill.
- Preheat oven to 425°F. Bake gratinata uncovered until cheese is melted and broccoli tops brown, about 20 minutes.