Preheat oven to 350 degrees.
In a medium sized pan, melt butter over medium-high heat.
Once butter has melted, add onion, garlic powder and black pepper. Stir to cook until translucent, about two minutes. Set aside.
In a large mixing bowl, add broccoli, sour cream, milk, cheese, and rice. Stir to combine.
Add the onion mixture to the mixing bowl and stir once more.
Spray non-stick oil on a baking pan and spread rice mixture evenly. Top with breadcrumbs if you'd like.
Place baking pan in oven for 35 minutes.