In a large mixing bowl, combine melted unsalted butter, granulated sugar, and egg. Whisk until creamy and well-blended. Add buttermilk and red food coloring, stirring until smooth.

In a separate bowl, whisk together all-purpose flour, cocoa powder, baking soda, and salt until evenly mixed.

Gradually add the dry ingredient mixture to the wet ingredients, gently folding them together until just combined.

Cover the dough with plastic wrap and place it in the refrigerator for at least 30 minutes.

Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper. Drop heaping tablespoons of dough onto the sheets, leaving space between cookies. Bake for 10-12 minutes.

Allow the cookies to cool on the baking sheets for about 5 minutes before transferring to a wire rack. Frost each cookie with cream cheese frosting once cooled.