For the cake: 

1. Preheat the oven to 350°F. Prepare two 8-inch round baking pans, line the bottom with parchment paper and grease the sides. Prepare your bake even strips if desired.
2. In a large mixing bowl, combine the sugar, vegetable oil, eggs, and vanilla extract. Beat on medium speed until well incorporated. Scrape down the bowl as needed. Next mix in the sour cream and beat until well combined.
3. In a separate bowl combine the remaining dry ingredients and sift together the flour, baking powder, and salt. Add half the dry ingredients, and half the milk, and beat on low speed just until the flour starts to incorporate. Repeat until all ingredients are added and combined. Use a spatula to scrape down the sides of the bowl and stir the batter from the bottom to the top to ensure it’s well mixed.
4. Divide the batter evenly between the pans, about 2 1/2 cups per each pan. Bake at 350°F for 28-32 minutes. Test the cake for doneness by inserting a toothpick into the center of the cake. If the toothpick comes out clean, the cake is done. Remove from the oven and allow to cool completely.

For the frosting: 

1. Cut butter into pieces. Using the paddle attachment, whip the butter for 5-7 minutes, scraping down the bowl occasionally. Beat until the butter looks light in color.
2. Add the powdered sugar 2 cups at a time, alternating in the liquid ingredients (heavy cream and vanilla). Mix on low speed until incorporated into butter then add the vanilla extract and mix to combine. Beat for about 60-90 seconds before adding additional powdered sugar.
3. Once all the ingredients have been added, increase speed to medium-high and beat for another 3-5 minutes to whip additional air into the frosting.

To assemble the cake

1. Use a cake leveler to cut the domes off the top of the cake. Place a dollop of frosting on your cake board and place the bottom layer of cake on top of that.
2. Place about 2 cups of frosting in a large piping bag fitted with a large open round tip, or simply cut off the end of the piping bag. Pipe a layer of frosting on top of the cake, starting at the outside edge and working your way into the middle. Spread evenly with an offset spatula. Place the next layer on top.
3. Use your piping bag to fill in any gaps between your layers and to create a crumb coat. Using an offset spatula or icing smoother, wipe away the excess frosting, leaving you just enough to coat the outside of the cake. Do not mix your crumb-coating frosting back into your icing if it has cake debris in it.
4. Proceed to frost the top and sides of the cake using your offset spatula. Once the sides of the cake are covered, use you icing smoother to remove any excess frosting.