Lemon Blueberry Cupcakes (gluten free or regular)

1 basic vanilla cake mix (gluten-free or regular)
1 small vanilla instant pudding mix
1 cup sour cream
1 cup vegetable oil
1/2 cup milk
4 eggs, beaten
1 teaspoon vanilla extract
1 teaspoon lemon extract
Zest of two lemons
3/4 cup blueberries, tossed in two tsp. reserved cake mix or two tsp. gluten-free or regular flour

Combine the first seven ingredients in mixer bowl; mix on low speed until moistened, then mix on medium speed for two minutes.  Add the lemon zest, and mix briefly until combined.   With a rubber spatula, fold in the blueberries.  Be sure to coat them with cake mix or flour so they don't bleed in the cake.  

Fill cupcake liners.  Depending on the size of your cakes, bake 15-20 minutes or until pick inserted comes out clean.  DO NOT OVERBAKE!  Remove from oven and allow to cool.  

Lemon Curd:
1/2 cup unsalted butter
1/2 cup lemon juice
zest of two large lemons
3/4 cup granulated sugar
1 teaspoon cornstarch
pinch of salt
6 large egg yolks
Melt the butter in a medium sauce pan over medium-low heat.  Remove from heat and add the lemon juice and zest.
Mix together the sugar, salt and cornstarch and add it to the pan.  Whisk in the egg yolks until smooth and return to heat. Cook over medium-low heat for roughly 10 minutes until the mixture has thickened and coats the back of a spoon. Do not allow the mixture to boil.
Once thickened, strain the mixture though a fine mesh strainer into a large bowl. Allow to chill in the refrigerator completely before using.

Lemon Cream Cheese Frosting:
8 ounces cream cheese, room temperature
1 cup unsalted butter, room temperature
1 teaspoon vanilla extract
1/2 teaspoon lemon extract
2/3 cup lemon curd (recipe above)
Zest of two lemons

To assemble, take cooled cupcakes and core a hole in the middle (you can use a vegetable peeler to make a small indention in the center of the cupcake).  Fill hole with lemon curd.  Use a decorating tip (Wilton 1M) on a pastry bag to pipe icing on the top, then garnish as desired.