Preheat oven to 350°F (175°C). Grease and line a 9x5-inch loaf pan.
Whisk flour, cocoa powder, baking powder, baking soda, and salt in a medium bowl.
Cream butter and sugar until light and fluffy, about 3–4 minutes.
Beat in eggs and vanilla extract until smooth.
Mix in sour cream and milk until fully combined.
Gradually fold in dry ingredients until just combined.
Fold in chopped chocolate and cherries.
Pour batter into loaf pan and smooth top. Bake 50–60 minutes until a toothpick comes out clean. Cool on wire rack.
Whisk powdered sugar, cherry juice, vanilla, and optional coloring until smooth. Drizzle over cooled loaf.
Slice and serve. Store leftovers in an airtight container up to 3 days.