1. Preheat oven to 350°.
2. To prepare the cupcakes, place 30 paper muffin cup liners in muffin cups; coat with cooking spray.
3. Weigh or lightly spoon cake flour into dry measuring cups; level with a knife. Combine cake flour, unsweetened cocoa, baking soda, baking powder, and salt in a medium bowl; stir with a whisk. Place granulated sugar and unsalted butter in a large bowl; beat with a mixer at medium speed until well blended (about 3 minutes). Add eggs, 1 at a time, beating well after each addition. Add flour mixture and 1 1/4 cups nonfat buttermilk alternately to sugar mixture, beginning and ending with flour mixture. Add white vinegar, 1 1/2 teaspoons vanilla, and food coloring; beat well.
4. Spoon batter into prepared muffin cups. Bake at 350° for 20 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on wire rack; remove from pan. Cool completely on wire racks.
5. To prepare frosting, beat 5 tablespoons butter, 4 teaspoons nonfat buttermilk, and cream cheese with a mixer at high speed until fluffy. Gradually add powdered sugar; beat until smooth. Add 1 1/4 teaspoons vanilla; beat well. Spread frosting evenly over cupcakes.