Lay the pineapple spears on a pan. Sprinkle lightly with cinnamon.
Whisk together the butter, brown sugar and cinnamon. (If it seems thick, I always put it in the microwave for a few seconds so that it can easily pour on top of the pineapple.)
Spread on top of the pineapple using a cooking brush.
Grill for about 7-10 minutes or until it is starting to turn golden brown.