Preheat oven to 350 degrees F (175 degrees C). Grease two 8 inch round cake pans.
Prepare cake mix according to package directions, replacing the water with reserved pineapple juice. In a bowl, cream together the butter, brown sugar and cinnamon. Stir in the pineapple and nuts.
Divide the pineapple mixture evenly between the prepared pans, then cover each pineapple layer with the cake mix batter.
Bake in the preheated oven for 25 minutes, or until a toothpick inserted into the center of the cake comes out clean. Cool cakes for 5 minutes, then turn one layer out onto a plate scraping off any pineapple that may be stuck. Next, invert second cake layer onto the first so there is pineapple in the middle and on top of the cake. May be served warm with whipped cream, if desired.