Step 1

Preheat oven to 350°F. Line four 7" or three 8" pans with parchment rounds, and grease with non-stick baking spray.

Step 2

Mix together 3 cups all purpose flour, 3 cups sugar, 2 1/2 tsp baking powder and 1 tsp salt in a stand mixer with a paddle attachment or hand mixer until fully combined.

Step 3

Mix in 1 cup of unsalted butter slowly into the dry ingredients on a low speed. Continue to mix until no large chunks of butter remain and the mixture looks crumbly.

Step 4

Pour in 1 cup of egg whites and mix on low until just incorporated. Mix in 1 1/2 cups buttermilk in two installments, on a low speed.

Step 5

Add in 2 Tbsp of vegetable oil and 2 tsp of vanilla extract and mix at a low speed until fully incorporated.

Step 6

If you plan to color your cake layers, add in the gel food coloring with the vanilla and oil.

Step 7

Scrape down the sides of the bowl with a rubber spatula, then beat on a low speed for about 30 seconds to make sure everything is properly mixed together.

Step 8

Divide the batter evenly between your prepared pans.

Step 9

Bake for 33-35 minutes or until a toothpick comes out with a few moist crumbs.

Step 10

Allow the pans to cool for 10 minutes, then run a small offset spatula around perimeter of the pan to separate the cake from the pan.

Step 11

Place cake layers into the freezer for 30 minutes to accelerate the cooling process. Once the layers are fully cooled, carefully flip the pans and remove the layers.

Step 12

Use a serrated knife to level the tops of the layers right before you plan to assemble your cake, or you can wrap and freeze them in you're making them in advance.

Step 13

If you make these cake layers in advance and freeze them, let them thaw for about 20 minutes before making your cake. The cake layers should still be slightly cold to the touch, which will make it easier to assemble your cake.

Step 14

While the cake layers bake and cool, make the vanilla buttercream frosting.

Step 15

Beat 3 cups of unsalted butter on a medium speed for 30 seconds with a paddle attachment, until smooth.

Step 16

Mix in 1 Tbsp of vanilla extract or vanilla bean paste and 1 tsp salt on a low speed.

Step 17

Slowly add in 11 cups of powdered sugar, 1 cup at a time. Alternate with small splashes of 1/3 cup of cream.

Step 18

Continue to mix on low speed for a few minutes, until the desired consistency is reached.

Step 19

If the frosting is too thick, add in additional cream (1 TBSP at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).

Step 20

If you plan to color the buttercream, add in the gel food coloring once the frosting is fully made, and beat on low until it reaches the desired color

Step 21

Stack and frost cake layers on a greaseproof cake board, using a dab of frosting to help stick the first cake layer to the board.

Step 22

Add an even layer of buttercream between each cake layer with a large offset spatula.

Step 23

Add a thin coat of frosting around the cake, fully cover the cake layers.

Step 24

Smooth using a bench scraper, then chill the cake in the fridge (20 minutes) or freezer (5 minutes) until the frosting is firm to the touch.

Step 25

Add a second, thicker layer of frosting to the cake, and smooth using a bench scraper. Then decorate as desired!