Preheat oven to 350 degrees. Spray 3 6" cake pans with non-stick spray and line the bottoms with parchment paper rounds. Set aside.
In a small bowl whisk together the flour, cocoa powder, baking powder, baking soda and salt. Then set aside.
To a large bowl add the softened, unsalted butter and granulated sugar. Cream together with an electric mixer until fluffy, 1-2 minutes.
Then add in the eggs and vanilla. Mix until pale in color and smooth, 1-2 minutes.
Alternate adding the dry ingredients and the kefir to the eggs/butter/sugar mixture until all is just combined and the batter is smooth. (Scrape down the sides of the bowl as necessary.)
Lastly, fold in the red gel food coloring just until combined.
Divide the batter evenly among the cake pans.
Bake the cakes for 28-32 minutes, or until a toothpick comes out clean from the centers.
Let the cakes cool in their pans for 5 minutes, then transfer to a cooling rack to completely cool.