Preheat your oven to 350°F (175°C) and line your muffin pan with cupcake liners, this saves you from sticky messes later. In a big bowl, sift together the cake flour, cocoa powder, and salt, then whisk to blend everything nicely.
In another bowl, beat the butter until soft and fluffy. Add the sugar and mix until creamy, this step is what makes your cupcakes tender and light.
Crack in the egg and pour in the vanilla, mixing until smooth. In another cup, whisk together the sour cream and red food coloring to achieve that iconic hue with a hint of tang.
First, add a third of the dry ingredients, then gently fold in a third of the sour cream blend. Keep alternating until just combined, don’t overmix, you want fluffy cupcakes!
Stir the baking soda into the vinegar (watch it fizz!) and quickly fold it into the batter to help them rise perfectly.
Fill each cupcake liner about two-thirds full, no overfilling! Bake for17 minutes, then let the cupcakes rest in the pan for 5 minutes before transferring to a wire rack to cool completely. This helps them set up nicely for frosting.
For the frosting, beat the softened butter until light and fluffy. Blend cream cheese and vanilla until creamy. Slowly beat in the powdered sugar, starting low to avoid a sugar cloud and then increasing speed until creamy.
Taste and tweak with a little extra vanilla or salt if you like. Spread or pipe onto cooled cupcakes and enjoy!