How to Make It
Make the Cupcakes: Preheat oven to 350°F. Sift together flour, cocoa powder, baking soda, and salt. Set aside.
In a mixer, beat together buttermilk, sugar, brown sugar, egg, food coloring, vinegar, and vanilla extract until well combined, about 2 minutes.
Add dry ingredients to wet ingredients and mix until just combined, about 1 minute. Scrape down sides and bottom of the bowl with a spatula and be sure to incorporate any unmixed batter stuck to the sides.
Place 12 paper baking cups in a 12-cup standard-size muffin pan, and divide batter evenly among baking cups (filling about two-thirds full). Bake until a toothpick inserted into the center comes out clean, 20-22 minutes. Allow to cool completely before frosting, about 1 hour.
Make the Frosting: Beat together cream cheese and butter on medium speed until well combined, about 3 minutes. Add powdered sugar and vanilla and beat on low speed to combine, then increase speed to medium high and beat until fluffy and satiny, about 4 minutes.
Assemble: Apply frosting to the top of the cupcakes either using an offset spatula or a piping bag. Decorate each cupcake with blueberries.