To make the buttercream:
Beat butter until light and fluffy, about 5 minutes. Add vanilla and salt, beat for another 1-2 minutes.Sift in organic powdered sugar and beat until well-combined. Add food coloring and beat to combine.
To make the cake:
Preheat oven to 325. Butter and flour two 8” x 3” cake pans or three 8x2” cake pans (see notes).
In the bowl of a stand-mixer, beat butter and sugar together for 5 minutes. Add salt, vanilla and nutmeg and beat for another 3 minutes.
Add eggs, one at a time, beating for at least a full minute to ensure incorporation. Scrape the bowl and beat again.
In a separate bowl, whisk together the cake flour and baking powder.
Add the dry mixture to the butter mix and beat on low to combine.While the flour is incorporating, add the sour cream and milk. Scrape bowl to ensure your batter is fully blended.
Divide equally between two prepared pans. Bake for 45-55 minutes, until tester comes out clean.