Preheat the oven to 350°F (175°C).
Steam the broccoli florets until tender, about 5-7 minutes.
In a large mixing bowl, combine the steamed broccoli, shredded cheddar cheese, sour cream, mayonnaise, garlic powder, onion powder, salt, and pepper.
Transfer the mixture into a greased baking dish, smoothing the top with a spatula.
Sprinkle breadcrumbs evenly on top of the casserole.
Bake in the preheated oven for 25-30 minutes, or until the top is golden and bubbly.
Let the casserole cool for a few minutes before serving.