Adjust the oven rack to 2nd level position (just above center) and preheat your oven to 350ºF. Line 2 cupcake tins with up to 18 cupcake liners. If using standard cupcake liners, you will yield closer to 15 cupcakes.
In a medium size bowl, whisk together the all-purpose flour, unsweetened cocoa powder, and baking soda. Set aside.
Using your hand mixer or stand mixer fitted with a paddle attachment, beat the unsalted butter and sugar together on medium-high speed until light in color and fluffy in texture.
Add in the eggs, vanilla extract, and sour cream, mixing until fully blended.
Switching the mixer speed to low, alternatively add in whisked dry ingredients with the milk. Mix until just combined. The batter will be on the thicker side, but still very easy to scoop and place into the cupcake liners.
With your mixer on low speed, add in enough red food dye to get a nice bright red color. I used 8-10 drops using the Wilton Color Right red. The number of drops will vary based on what brand you use.
With a 1 ½ tablespoon-size cookie scoop or 2 spoons, fill the cupcake liners ⅔ full.
Place in the oven and bake for 20-22 minutes at 350ºF or until an inserted toothpick comes out clean. The cupcakes should have a nice dome shape to them.
When done, allow the cupcakes to cool for approx. 5-10 minutes before transferring them to a cooling rack. Frost the cupcakes once they have completely cooled.
Unfrosted cupcakes can be kept in an airtight container for up to 3 days at room temperature.