Make the Cupcakes
Preheat the oven to 350º. In a large bowl, whisk together the coconut flour, baking powder, and salt until blended. Whisk in the eggs, agave nectar, oil, milk and vanilla until completely blended and smooth.
Divide the batter equally between lined muffin cups and bake for 20 minutes, or until golden and a toothpick inserted in the center comes out clean. Transfer the baking tin to a wire rack and let the cupcakes cool for 10 minutes. Carefully remove the cupcakes from the tin and place on the wire rack to cool completely.
Meanwhile, Make the Frosting
In a large mixing bowl or stand mixer, beat together the butter, confectioners’ sugar, milk, lime juice, one teaspoon of zest, vanilla and salt until smooth and fluffy, about 3 minutes. Frost the cupcakes, garnish with the remaining lime zest and shredded coconut, and serve or store in an airtight container for up to two days.