Preheat oven to 375 degrees F. and line muffin tins with paper cups.
Sift flour, 1 cup of sugar, baking powder and salt into a large mixing bowl. Make a well in the center of the flour mixture and add oil, buttermilk, vanilla and tangerine zest. Beat one minute with electric beaters. Add tangerine juice and egg yolks and beat another minute.
In a separate bowl and using cleaned beaters, whip egg whites until foamy. Gradually pour in remaining ½ cup sugar and whip until whites hold a stiff peak. Fold whites gently into batter and spoon into muffin cups. Bake for 15 minutes or until cupcakes spring back when pressed. Allow to cool.
For icing, beat butter until fluffy. On low speed beat in icing sugar until smooth. Beat in vanilla, zest and tangerine juice. If icing is too thin, add a touch more icing sugar. Spread icing onto cupcakes, garnish with sprinkles and serve.