Preheat the oven to 350ºF and line two cupcake pans (or a muffin pan will do) with paper liners. You can also bake one pan at a time if you only have one cupcake pan. This recipe will make about 24 cupcakes.
Combine the vanilla and buttermilk in a separate measuring cup and set it aside.
Next, add the eggs and oil to a separate bowl then whisk and set them aside.
Add the cake flour, sugar, salt, baking powder, and baking soda to the bowl of your stand mixer with the paddle attachment. You can use a large bowl and an electric mixer if you don’t have a stand mixer, just mix for longer. Use these photos as a guide instead of mixing by time.
Then add the softened butter to the rest of the dry ingredients and mix on low until the mixture resembles a sandy texture. Depending on how soft your butter is, this might take a minute or two.
Pour the milk mixture into your dry ingredients and increase the speed to medium (speed 4 on a KitchenAid, speed 2 on a Bosch). Mix for 1 ½ minutes to develop the fluffy structure of the cupcake. The batter will go from being yellow to a fluffy white.
Slowly add your egg mixture in three parts and mix on low until it's fully combined.
Fill your liners ⅔ of the way full with the cupcake batter. I use my kitchen scale to measure out 1.5 ounces of batter per cupcake.
Bake the cupcakes for 15-20 minutes or until they are just starting to turn golden brown and the center of the cupcake springs back when you lightly touch it. I rotate my cupcakes halfway through baking for even browning. If you’re making mini cupcakes, bake for less time.
Let your cupcakes cool in the pans for five minutes, then move them to a cooling rack to cool completely.
Place your favorite frosting into a piping bag with a tip, I like a 1M or a 2F, and pipe a swirl on top. I love using my easy vanilla buttercream and topping them with a few sprinkles. Swiss meringue buttercream or strawberry buttercream would also be delicious.