To make candied blood oranges, preheat oven to 200°F (100°C).
Combine blood orange juice and sugar in a small saucepan over medium heat. Stir to dissolve sugar and bring to a boil. Add orange slices and simmer for 12 to 15 minutes or until skin is tender and translucent.
Remove with a slotted spoon and place in a single layer on a parchment-lined cookie sheet. Place in oven and cook for 90 minutes. Remove to a cutting board; while still warm slice each round into several small triangles. Allow to cool completely. (Candied blood orange will keep, tightly covered in a single layer, for up to a week.)
For cupcakes, preheat oven to 350°F (180°C).
Prepare a 12-cup muffin tin with paper liners.
Using an electric mixer, cream butter, sugar, blood orange zest and vanilla until light and fluffy, about 3 minutes. Continue beating and add eggs, 1 at a time.
Combine blood orange juice and water; set aside. In a separate bowl combine flour, baking soda, baking powder and salt. Add to creamed mixture alternately with orange juice mixture, stirring well after each addition.
Divide batter between 12 cups and bake for 20 to 22 minutes or until a tester comes out clean. Allow to cool completely before frosting.
To make frosting, place egg whites, cream of tartar and salt in a large mixing bowl; set aside.
In a small saucepan, combine sugar with water over medium-high heat. Stir to dissolve sugar and bring to a boil. Cook until mixture reads 238°F (114°C). Remove from heat.
Using an electric mixer, beat egg white mixture to medium peaks. Reduce speed to low and slowly pour hot syrup into the egg whites in a thin stream down the side of the bowl. Gradually increase the speed to high and continue to beat for 4 to 5 minutes, or until mixture is thick and glossy. Add vanilla extract and continue to beat until just combined.
Using a pastry bag fitted with a large star tip, pipe icing into generous mounds onto each cupcake. If you wish, lightly toast marshmallow cream with a small kitchen torch. Decorate cupcakes with candied was blood orange pieces.
Recipe adapted from: St. Onge, Christopher. "Orange Cupcakes with Marshmallow Cream Frosting." Food & Drink. Holiday 2012.