Preheat the oven to 350°F. In a large mixing bowl, cream together the butter and sugar until light and fluffy. Add eggs one at a time, beating well after each addition. Mix in the lemon juice and zest. In a separate bowl, whisk together flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, alternating with the milk, until a smooth batter forms.

Divide the batter evenly among the lined cupcake pan. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool completely on a wire rack before filling.

In a saucepan, combine lemon juice, zest, sugar, and egg yolks. Cook over medium heat, stirring constantly, until the mixture thickens and coats the back of a spoon. Remove from heat and stir in butter until melted. Let cool completely before using.

In a clean bowl, beat the egg whites until soft peaks form. Gradually add sugar, continuing to beat until stiff, glossy peaks form.

Once the cupcakes are cooled, use a small spoon to scoop out the center of each cupcake. Fill with lemon curd. Pipe or spread meringue over the top of each cupcake.

Using a kitchen torch, carefully toast the meringue until golden brown. Serve immediately for the best texture and flavor.

Store any leftover cupcakes in an airtight container in the refrigerator for up to 3 days. Allow to come to room temperature before serving.