Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius). Grease 2 6-inch cake pans with non-stick baking spray, and line them with parchment paper rounds.
Add the cake flour, sugar, baking powder, baking soda, and salt to the bowl of a stand mixer fitted with the paddle attachment. Mix on low, spinning about 5 times.
1 ½ cup cake flour, 1 cup granulated sugar, 1 teaspoon baking powder, ¼ teaspoon baking soda, ¼ teaspoon salt
Add the butter to the bowl and beat on low for 5 minutes until the texture looks like wet sand.
⅓ cup unsalted butter
Add the oil, egg, egg white, and vanilla extract. Mix on low until a batter forms. Then pour in the buttermilk and mix until well combined.
⅓ cup vegetable oil, 1 large egg, 1 egg white, 2 teaspoon vanilla extract, ⅔ cup buttermilk
Portion the batter evenly between the 2 cake pans. Place the pans on the center rack and bake for 25-30 minutes. The cakes are done when the center springs back after lightly pressing with your finger.
Remove the cakes from the oven let them cool for 20 minutes on a wire cooling rack. Then, gently turn the pans upside down onto the rack and let them cool to room temperature.
Cream Cheese Frosting
In a large bowl, beat the softened butter and cream cheese together with an electric mixer on medium-high speed until smooth and fluffy.
½ cup unsalted butter, 8 ounces cream cheese
Gradually add the powdered sugar to the mixture, one cup at a time, beating well on low after each addition.
4 cups powdered sugar
Add the vanilla bean paste and salt and mix on low until well combined.
2 teaspoons vanilla bean paste, ¼ teaspoon salt
Assembly
Assemble the cake when the layers are completely cool. If the cakes have domed tops, level them with a cake leveler or serrated knife.
Spread a thin crumb coat of frosting over the entire cake. Refrigerate for 20 minutes.
Once the frosting has firmed cup, cover the cake with another layer of frosting. Pipe a boarder around the cake if desired. Decorate with sprinkles, slice, and enjoy!
Video
Notes
I recommend using a food scale for accuracy. If you don't have one, fluff up the flour first before spooning it into your measuring cup.
Use room temperature eggs, butter, and buttermilk for a fully blended, smooth batter that bakes up evenly.
Don't overmix. Overmixing cake batter will result in a dense cakes with a sunken center.
Wait for the cake layers to cool completely before frosting them. The frosting will melt off if they're too warm.
Storage: Frosted vanilla cake keeps in the refrigerator for up to 1 week stored in an airtight cake carrier. Cover the cut section with leftover frosting to keep it moist.Freezing: Wrap leftover cake slices in plastic wrap and place them in an airtight, freezer-safe container. The slices will keep in the freezer for up to 3 months. When ready to enjoy, unwrap a slice and let it thaw on the counter for about 1 hour.