Step 1

Preheat oven to 350F (175C). Line muffin pans with paper cupcake liners.

Step 2

In a large mixing bowl, beat the egg, oil, kefir, red food coloring and vanilla extract. Fold in sugar and salt.

Step 3

Sift flour and cocoa powder into the same bowl and whisk until combined.

Step 4

Mix baking soda and vinegar in a small measuring cup and add in the batter when the mixture is still bubbling.

Step 5

Using an ice cream scoop, fill the liners 2/3 of the way. Bake for 18 minutes or until a toothpick comes out almost clean, just with some crumbs on it. Cool the cupcakes for 5 minutes in the pan and then transfer onto a cooling rack to cool completely.

Step 6

To make the frosting, using an electric mixer, beat the room temperature butter for 5 minutes until it has become light and airy, lost most of its color and doubled in size. Add the powdered sugar half cup at a time and beat for about a minute in between each addition. Thin out the consistency with milk, adding a teaspoon at a time.

Step 7

Transfer the frosting into a pastry bag and frost the cupcakes when they are completely cooled.