Mix brown sugar, chili powder, cinnamon and cayenne pepper in a small bowl and set aside.
Combine popcorn and almonds in a large bowl. Place butter in a small bowl and microwave for 30 seconds. Stir and then microwave for another 30 seconds.
Pour over popcorn and almonds, stir and then toss with half of brown sugar mixture. Stir, taste and add more of the brown sugar mixture to taste.