Preheat oven to 350°F. Spray a 9x13-inch cake pan with nonstick spray. Set aside.
In a large mixing bowl with an electric mixer, beat together the cake mix, pudding mix, sour cream or yogurt, oil, water, eggs, and vanilla for 1-2 minutes or until well combined.
1 (15.25-ounce) box spice cake mix, 1 (3.4-ounce) box instant vanilla pudding mix, ¾ cup sour cream or plain Greek yogurt, ¾ cup vegetable oil, ½ cup warm water, 3 large eggs, 2 teaspoons vanilla extract
Spread the cake batter evenly into the bottom of the prepared pan. Set aside.
In a medium bowl, whisk together the pumpkin, eggs, brown sugar, pumpkin pie spice, vanilla, and salt until smooth and well combined.
1 (15-ounce) can pure pumpkin puree, 2 large eggs, 6 tablespoons lightly packed brown sugar, 2 teaspoons pumpkin pie spice, 1 teaspoon vanilla extract, Pinch of salt
Spread the pumpkin mixer on top of the cake batter. Swirl the end of a butter knife, skewer, or chopstick through the assembled cake; you won’t notice much of a difference visually, but this will help as the cake is baking.
Bake for 45-50 minutes, or until a toothpick inserted into the center comes out with only a few moist crumbs clinging to it. Allow the cake to cool. If desired, dust the top with powdered sugar before serving with a dollop of lightly sweetened whipped cream.
Notes
Ingredients
Any neutral oil, such as avocado oil, can be used in place of the vegetable oil.
Make sure to buy pure pumpkin puree, not pumpkin pie filling.
If you don't have pumpkin pie spice on hand, substitute with 1 1/2 teaspoons ground cinnamon, 1/4 teaspoon ground ginger, and 1/4 teaspoon ground cloves.
Storage
Store covered at room temperature for 1-2 days or in the refrigerator for 3-4 days.