Drain pineapple, reserving 1/3 cup juice and 6 pineapple rings (save remaining juice and pineapple for another use).
Combine butter, brown sugar, vanilla, cinnamon and nutmeg.
Brush half of the mixture on both sides of pineapple rings and cake slices.
On an uncovered grill over medium heat, cook pineapple and cake for 1 to 2 minutes on each side or until golden brown, brushing occasionally with remaining pineapple juice mixture.
Top each slice of cake with a pineapple ring. Top with raspberries, nuts and whipped cream, if desired. Serve immediately.