Stir the brown sugar, salt, and cayenne pepper in a small bowl. Set aside.
Coat a large pot with canola oil, place 2-3 popcorn kernels and cover. Place over medium high heat. When you hear the kernels pop, add all the remaining kernels to the pot, replace the lid, and shake over the heat until all the corn is popped. When you no longer hear popping, remove from heat and transfer to a large bowl. Toss in the sugar-salt-spice mixture and butter (optional) and mix well. Enjoy while toasty!