Preheat oven to 350* degrees F. Line 2 muffin tins with about 18 paper liners. Set aside. Meanwhile, prepare the cake mix according to package directions on back of box. Stir in the lemon dry pudding mix to incorporate.
Fill each muffin tin about 3/4 of the way full with the batter. Bake for approx. 15-18 minutes or until a toothpick inserted near the center comes out clean or with moist crumbs. Cool the cupcakes completely.
Using a small paring knife or a cupcake corer, core the cupcakes and discard centers, being careful not to puncture through the cupcake's bottom. You only want to core about halfway through the cupcake. Fill with some of the lemon pie filling.
Now, to make your frosting: In the bowl of a stand mixer, cream together butter, vanilla extract, and 1/3 cup of the lemon pie filling until fluffy, about 2 minutes. Add in the powdered sugar, one cup at a time, until frosting is light and fluffy. You may not need all of the powdered sugar. If frosting becomes too thick, add in a little more lemon pie filling.
Spoon the frosting into a piping bag attached with a large open-star tip. Begin piping the frosting onto the cupcakes, taking care to cover the lemon filling in the center. Sprinkle immediately with the yellow sanding sugar. Serve immediately, or store cupcakes airtight at room temperature for up to a day, or airtight in the fridge for up to 3 days.