How to Make It
Preheat oven to 425°F. Toss together frozen broccoli, black pepper, 1 1/2 tablespoons of the oil, 1/2 teaspoon of the salt, and 1/4 teaspoon of the red pepper on a rimmed baking sheet. Spread broccoli mixture in a single layer. Bake in preheated oven until charred and browned in spots, 30 to 35 minutes, stirring after 15 minutes.
Heat 1 1/2 tablespoons of the oil in a large skillet over medium. Add breadcrumbs and 1/4 teaspoon of the salt. Cook, stirring often, until golden brown, 5 to 6 minutes. Remove from skillet; set aside. Wipe skillet clean.
Bring a large pot of water and 1 tablespoon of the salt to a boil over high. Cook bucatini until al dente, about 7 minutes. Drain, reserving 1 cup cooking liquid.
Heat garlic, remaining 1/4 cup oil and 1/4 teaspoon red pepper, and, if desired, anchovies in skillet over medium. Cook, stirring often, until garlic is lightly golden, 3 to 4 minutes. Add pasta; cook, stirring constantly and gradually adding cooking water, until sauce has thickened, 2 to 3 minutes. Stir in broccoli mixture and remaining 1/4 teaspoon salt. Divide pasta among 4 serving bowls; top with toasted breadcrumbs.