Melt brown sugar, butter and cinnamon together. Be sure the brown sugar is fully dissolved.
Lightly brush both sides of the pineapple with vegetable oil, and place directly on the hot grill.
After 2 – 3 minutes, flip the pineapple over and continue cooking for another 2 – 3 minutes.
When grill lines appear and pineapple is done, remove from heat and brush with brown sugar, butter and cinnamon mixture.
Top with a dash of cayenne pepper, if using.
Serve and enjoy immediately.