Preheat oven to 150 degrees fan and line a 12 cup muffin tray with cupcake liners
Using an electric mixer cream together butter and sugar.
Add in eggs one at a time beating thoroughly before adding the next
In a small dish mix together cocoa and coloring mix well, until very smooth then add into your bowl. Mix well
Add half of your flour and buttermilk and mix through then add the remaining flour and buttermilk. Mix until just combined
In a small dish (just use the one you mixed your cocoa in) quickly mix together baking soda and lemon juice before adding to your cake batter. Mix through using a spatula and pour into your prepared cake pan.
Bake for 25 - 30 minutes or until your cupcakes are just baked through.
Remove your tray from the oven and allow the cupcakes to cool fully before finishing with with your choice of icing