Make the Cake:
Preheat oven to 350F and spray a 12-cup Bundt pan very well with floured cooking spray or grease and flour the pan; set aside.
To a large bowl, add all ingredients and beat with a handheld electric mixer on low speed for about 30 seconds and then beat on high until well blended and combined.
Turn batter out into prepared pan and bake for about 40 to 45 minutes, or until done. A toothpick inserted should come out clean or with a few moist crumbs but no batter. Allow cake to cool in pan for about 10 to 15 minutes before inverting onto a cake stand or platter. Allow cake to cool completely before frosting it so the frosting doesn’t melt.
Make the Frosting:
To a large bowl, add the pudding mix, milk, and beat with a handheld electric mixer on medium-high speed until combined and it begins to thicken; about 2 to 3 minutes.
Add the whipped topping and beat to incorporate, about 2 minutes. Evenly add frosting to the cake. I just added it to the top but you can spread it down the sides and center if desired.
Evenly garnish with pistachios and serve immediately. Cake will keep airtight in the fridge for up to 4 days.