1. Combine brown sugar, Cajun seasoning mix, garlic powder, onion powder and chili powder in a small bowl.
2. Melt ¼ cup butter. Cool slightly, then pour off the clear melted butter layer into a small bowl. Discard the opaque milky solids that remain behind.
3. Stir the liquid smoke into the butter.
4. Place popcorn in a large bowl, and drizzle it with butter mixture. Toss to coat the popcorn well.
5. Sprinkle sugar-seasoning mixture over popcorn and toss to distribute evenly.
6. Serve immediately or store in an airtight container.
Liquid smoke can be found with the barbecue sauces/condiments section of large grocery stores.