Step 1Heat the oven to 350 degrees. Spread the coconut on a baking sheet and toast until lightly browned, stirring once or twice, 10 to 12 minutes. Set aside.
Step 2Prepare the cake mix and bake in a bundt pan according to package directions. Cool.
Step 3Combine the crushed pineapple and sugar in saucepan and bring to boil over medium heat about 3 minutes. Cool slightly.
Step 4Prepare the pudding mix according to the package directions. Cool.
Step 5Cut the cake in half horizontally Spread half the pineapple mixture on top of the cut bottom half. Top with half of the pudding. Carefully replace the top half of the cake and top it with the remaining pineapple mixture, then the pudding. Pierce holes in the cake with a fork. Chill the cake at least 1 hour.
Step 6Just before serving, whip together the whipping cream and powdered sugar and cover the cake with it. Sprinkle the cake with the coconut. If desired, garnish with pineapple slices.