Key Lime Cupcakes with Meringue

Ingredients:
24 paper liners for cupcake pans

For Cupcakes:
1 large lime, scrubbed (for 1 tsp zest)
4 large eggs
1 pkg (18.25 oz) plain yellow cake mix
1 pkg (3.4 oz) vanilla instant pudding mix
1 1/4 cups water
1/3 cup vegetable oil

For Filling:
1 can (14 oz) sweetened condensed milk
1/3 cup Key lime juice

For Meringue:
1/4 tsp cream of tartar
Reserved 3 large egg whites
1/3 cup granulated sugar

Directions:
Preheat oven to 350 degrees. Fill cupcake pans with liners.

Prepare the cupcake batter:
With a citrus zester or fine grater, zest the lime and reserve one tsp. Separate three of the eggs, place the whites in a large clean mixing bowl and the yolks in another mixing bowl. Add the remaining egg, cake mix, pudding mix, water, oil, lime zest and lime juice to the egg yolks. Blend with an electric mixer on low speed for 30 seconds. Stop the machine and scrape down the sides of the bowl then increase the mixer speed to medium and beat for 2 minutes. The batter should look well blended. Spoon or scoop 1/4 cup batter into each lined cupcake cup, filling it two thirds of the way full. Place the pans in the oven. Bake the cupcakes until they are lightly golden and spring back when lightly pressed with your finger, 18 to 22 minutes. Remove pans from the oven and place them on wire racks to cool for five minutes. Increase the oven heat to 450 dregrees.
Run a knife around the edges of the cupcake liners, lift the cupcakes up from the bottoms of the cups using the end of the knife, and pick them out of the cups placing them on a wire rack to cool for 15 mintues before filling.
Prepare the filling:
Place the sweetened condensed milk and Key lime juice in a small bowl and stir to combine. Spoon the mixture into a pastry bag fitted with a medium tip. Press the tip 1/4 inch into the center of the cupcake and squeeze the bag to release about 1 Tbsp filling into the cupcake. Scrape of any excess filling. Place the cupcakes back into the pan.
Prepare the meringue:
Add the cream of tartar to the reserved egg whites and beat with an electric mixer on high speed until frothy, 45 seconds. Add 1 Tbsp of the sugar. Continue beating on high, adding one tablespoon sugar at a time, until the whites form stiff peaks. Spoon two tablespoons meringue onto the top of each cupcake and swirl to spread it just to the edges of the cupcakes. Place the pan in the oven and bake until the meringue in light nutty brown in color, five to six minutes.
Lift the cupcakes out of the pan and serve at once or allow the cupcakes to cool for 10 minutes, then serve.