Preheat oven to 180°C(350°F). Line muffin baking tray with cupcake liners. Set aside.
In a medium mixing bowl, whisk together flour, baking powder and salt. Set aside.
In another small bowl mix together sugar and lemon zest.
With a hand or stand mixer on medium speed, beat together softened to room temperature butter with lemon zest sugar, until light and fluffy, about 2-3 minutes.Scrape down the sides of the bowl with a rubber spatula, as needed. On medium speed beat in the eggs.
Turn to low speed, and add ⅓ of the flour mixture. Mix just until combined, add the second ⅓ of the dry ingredients and mix until just combined.Add the milk and lemon juice. Mix well.Add the last ⅓ of the dry ingredients. Mix just until combined. Spread the batter between the lined muffin tray cups, filling them about ⅔. It's about 1½ tablespoon per muffin cup.
Bake for about 15-20 minutes, or until toothpick inserted into the center of the cupcake, comes out clean.
Allow the cupcakes to cool in the pan, for a few minutes, then take them out and cool completely on a wire rack.
Scrape out the middles of the cupcakes, with a teaspoon, or a melon scraper.
Fill with previously prepared lemon curd. See notes below for recipe.
Top with Vanilla Swiss Meringue Buttercream. See notes below for recipe.
Enjoy!