Preheat the oven to 350 degrees Fahrenheit.
Spray and line two 8 or 9 inch round cake pans with parchment paper. I like to use these parchment rounds for convenience.
In a large mixing bowl or bowl of a stand mixer, beat together all wet ingredients. For best results, keep your eggs and milk at room temperature and melt your butter, then let it cool slightly.
Beat in the dry ingredients until a smooth batter forms, making sure to spoon and level the flour.
Add the batter to the prepared pans, trying to keep them as even as possible.
For 9 inch cakes, bake for 28-32 minutes or until a toothpick comes out clean. 30 minutes is usually perfect in my oven, but all ovens are different. For 8 inch cakes, bake for 30-36 minutes or until a toothpick comes out clean.
Remove from the oven and let cool in the pans for 15 minutes, then carefully flip onto a cooling rack to finish cooling.
If you want to frost it quickly, add the cakes to the fridge for an hour, otherwise just let cool at room temperature until completely cool. You can also let the cakes cool, wrap them in plastic wrap, place in the fridge and frost the next day.
To make the buttercream, cream the softened butter with an electric mixer, then beat in the sugar 1 cup at a time. Finally, beat in the milk, vanilla and salt. I replaced some powdered sugar with cocoa powdered to make a light chocolate, but regular vanilla is also a favorite!
When the cakes are cool, frost the cake, I like about 1 cup of frosting between each layer, and then 2 cups to cover the outside. The cakes will be slightly rounded in the middle, so I used a cake leveler to make them flat, but you definitely don't have to, they will still look great even with slightly domed tops!