Making the Cake

1. Preheat oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or a bundt pan.
2. In a large bowl, whisk together the cake mix and pistachio pudding mix.
3. In another bowl, whisk the eggs, vegetable oil, crushed pineapple (with juice), milk, and vanilla extract until combined.
4. Gradually add the wet ingredients into the dry mixture, stirring gently until just combined. Do not overmix.
5. If using, fold in the chopped pistachios.
6. Pour the batter evenly into the prepared cake pans.
7. Bake for 30-35 minutes (round pans) or 45-50 minutes (bundt pan), or until a toothpick inserted in the center comes out clean.
8. Let the cake cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Making the Frosting

1. In a mixing bowl, beat the cream cheese and butter together until smooth.
2. Gradually add the powdered sugar and vanilla extract, beating until light and fluffy.
3. Spread the frosting over the cooled cake and sprinkle with crushed pistachios.