1. Heat the oven to 180 degrees. In the meantime, place the baking cups in a muffin pan.
2. Beat the butter and sugar with an electric whisk until the mixture is frothy. Then add the egg, salt and vanilla extract.
3. Sift the flour with the cocoa into a bowl. Add half of this mixture to the butter and sugar mixture and half of the buttermilk. Whip the ingredients, then add the remaining flour and buttermilk. Continue beating until the mixture is uniform.
4. In another bowl, mix baking soda and vinegar, then add them to the mixture.
5. Pour the mixture into the cups. Bake the cupcakes in the oven for 20-25 minutes, then remove them and let them cool.
6. Prepare the decoration: whip the butter and sugar, then add the mascarpone, the icing sugar and the grated lemon zest.
7. Use a pastry bag to decorate the cupcakes with the cream made. Finish the decoration by spreading the heart-shaped confetti on the icing.