Preheat oven to 400°.
Arrange cauliflower in a single layer on a baking sheet coated with cooking spray. Coat cauliflower with cooking spray; sprinkle with salt and pepper. Bake at 400° for 25 minutes, turning cauliflower twice.
Melt butter in a small skillet over medium heat; cook 3 minutes or until lightly browned. Combine cauliflower and browned butter in a bowl, and toss gently to coat.