Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, or line them with parchment paper for easier removal.

Mix Dry Ingredients: In a large bowl, combine the vanilla cake mix, instant vanilla pudding mix, granulated sugar, baking powder, and salt. Stir until well combined.

Add Wet Ingredients: Add the vegetable oil, eggs, milk, and vanilla extract to the dry mixture. Mix using an electric mixer on medium speed for 2-3 minutes until the batter is smooth and well-combined.

Bake the Cake: Divide the batter evenly between the two prepared cake pans. Smooth the top with a spatula. Bake in the preheated oven for 28-30 minutes, or until a toothpick inserted into the center comes out clean.

Cool the Cake: Let the cakes cool in the pans for 10 minutes. After that, turn them out onto a wire rack to cool completely.

Cream the Butter: In a large bowl, beat the room-temperature butter using an electric mixer on medium speed until it’s smooth and creamy.

Add the Powdered Sugar: Gradually add the powdered sugar, about 1 cup at a time, and continue beating until fluffy and smooth.

Add Sour Cream & Vanilla: Mix in the sour cream, vanilla extract, and a pinch of salt. Beat until the frosting is light, fluffy, and spreadable. If it’s too thick, you can add a teaspoon of milk to loosen it up.

Once the cakes are completely cooled, place one layer on a cake stand or serving plate.

Spread a generous layer of frosting on top of the first cake layer.

Place the second cake layer on top, and then frost the top and sides of the entire cake.

If desired, decorate with sprinkles, berries, or any other toppings.