Preheat the oven to 350°F. Line a standard muffin pan with cupcake liners.
Finely grate the zest of the oranges. Squeeze the juice.
Whisk together the cake mix, eggs, vegetable oil, ⅓ of the grated zest, and ⅓ cup orange juice. Divide the batter evenly among the prepared muffin tins. Bake for 15-20 minutes or until a toothpick inserted into the center comes out clean. Let cool completely.
In the bowl of a mixer, preferably fitted with a paddle attachment, combine the vegetable shortening and Swerve Confectioners. Mix on low until fully combined. Add ½ the remaining orange zest. With the mixer on medium speed, add orange juice, 1 tablespoon at a time, until a light, spreadable consistency is achieved. Beat for another minute. Pipe or spread the frosting on the cooled cupcakes and sprinkle with the remaining zest.