Preheat oven to 350 degrees and grease a 9×13 baking dish.
In a large bowl, mix together the cake mix, pudding mix, oil, eggs, and pineapple with juices.
Beat until well combined.
Transfer batter to the prepared baking dish and bake for 30-35 minutes or until an inserted tooth pick comes out clean.
Allow cake to cool.
To make the frosting: Mix together the second pudding mix and milk until the mixture thickens.
Fold in the cool whip until fully combined.
Frost cake and chill for 2 hours before serving.
Top with chopped pistachios if desired.
PrepTime: 10 minutes | CookTime: 30-35 minutes | Total Time: 40-45 minutes | Calories: Approximately 200 calories per serving | Servings: 12 servings