1Preheat oven to 350 degrees. Prep 6 wells in a muffin tin with liners.
2In a large bowl, cream butter, sugar and zest. Add the egg yolk and mix thoroughly.
3Add the flour, baking powder and salt to the butter mixture.
4Add the sour cream and juice to the rest of the batter and beat till well combined.
5Fill each cupcake well 2/3 full.
6Bake for 12 to 15 minutes, do a toothpick test, if it comes out clean with just a couple of crumbs, remove them from the oven to cool briefly on a wire rack, then remove from the pan to cool completely before icing.
8Beat the egg whites and a pinch of salt, to form soft peaks using an electric mixer.
10Meanwhile, in a medium saucepan bring sugar, tangerine slices, juice and water to a boil, stirring occasionally.
11Continue to boil until it reaches a soft ball stage (when a drop of syrup forms a soft ball when dropped in cool water) while continuing to stir occasionally.
12Keep the mixer running, you'll need an extra set of hands.
13While you pour a continuous stream of the molten syrup into the egg whites, continue to beat for about 5 minutes or until frosting is fluffy, glossy and cool.
14Allow the tangerine slices to cool and harden on a wire rack.
15Frost the cooled cupcakes and top with candied tangerine slices.
16NOTE: IF THE ICING ISN'T ORANGE ENOUGH IN COLOR, YOU CAN ADD A DROP OR TWO OF FOOD COLORING.