Ingredients

• 1/2 cup Unsalted Butter at room temperature
• 2 cups Sugar
• 3 cups Gluten Free All Purpose Baking Flour
• 3/4 tsp Xanthan Gum
• 1 tsp Salt
• 1 tsp Baking Soda
• 4 Eggs at room temperature
• 1 cup Sour Cream at room temperature
• 1 tsp Vanilla Extract
• 2/3 cup Key Lime Juice (fresh or bottled)

• 1 cup Unsalted Butter at room temperature
• 2 cups Cream Cheese at room temperature
• 1-1/2 cups Powdered Sugar
• 1 tsp Vanilla Extract
• 1 Tbsp Key Lime's Zest (optional)

Instructions

1. Preheat the oven to 350°F. Line muffin pans with paper liners or mini muffin pans with mini liners.
   
   Cream the butter and sugar in the bowl of an electric mixer fitted with the paddle attachment on high speed until light and fluffy. On medium speed, add the eggs 2 at a time, then add the sour cream and vanilla. Scrape down the sides then add the key lime juice. Turn the speed to medium-low and beat for another minute. Stop the mixer.
   
   Sift together the flour, xanthan gum, salt, and baking soda in a bowl. With the mixer on low speed (stir), add the flour mixture to the butter mixture until just combined. Fill the cupcake liners to the 2/3 full with batter. Bake in the center of the oven for 20 – 25 minutes for full-size or 15 minutes for mini. They're done when a toothpick comes out clean. Cool to room temperature.
   
   While the cakes cool, make the icing. Mix the butter, cream cheese, sugar, and vanilla in the bowl of an electric mixer fitted with the paddle attachment, on low speed until the sugar incorporates, then turn it up to high and whip for about 3 minutes. Spread the frosting generously on top of each cupcake.
   
   For fancier frosting, put the icing in a gallon sized ziploc bag and refrigerate for 15 minutes. Cut the bottom corner of the bag and pipe a dot of frosting on, then pull up. Continue until the surface of the cake is covered. Add key lime zest on top for decoration. Makes 3 dozen full-size cupcakes.