In a mixing glass, combine the butter, brown sugar, cinnamon, and vanilla. Stir until smooth.
Place the pineapple slices in a mixing bowl and set aside.
On high, grill until the desired temperature is reached. Grill for about 2 minutes, until grill marks appear on the slices.
Turn each slice 90 degrees and cook for another two minutes. You should now have grill marks on the bottom as a result of this process.
Brush each slice with the remaining sauce and turn it over. Allow to grill for approximately 2 minutes, until grill marks appear. Each slice should be rotated 90 degrees after cooking for another 2 minutes.