Make the orange cupcakes:
Sift all the ingredients into a bowl and set aside.
In another bowl, beat all of the wet ingredients together until well-mixed.
Add the wet ingredients to the dry ingredients and mix with a whisk just until you have a smooth batter. Do not overmix or overbeat.
Divide the batter equally among 12 cups of a standard-sized muffin pan lined with cupcake liners.
Bake in a preheated 350-degree oven about 30-32 minutes or until a toothpick inserted in the center comes out clean.
Make the buttercream:
Cream together the butter and shortening until they are fluffy, about 1 minute.
Now add the orange juice, zest, liqueur and vanilla and half the sugar. Beat until mixed, then add the remaining sugar and beat until mixed. This should take no more than 2 minutes altogether.
Frost the cupcakes after they've cooled completely. I sifted some cocoa powder on the cupcakes after I was done, to get a really pretty look. It's completely optional, of course,