Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.

In a large mixing bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract. In a separate bowl, whisk together the flour and baking powder, then gradually add to the wet ingredients, alternating with the milk, until just combined.

Divide the batter evenly among the cupcake liners. Bake in the preheated oven for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool completely on a wire rack.

In a saucepan, combine lemon juice, lemon 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 the butter until fully melted and incorporated. Let cool completely.

In a clean, dry bowl, beat the egg whites and cream of tartar until soft peaks form. Gradually add the sugar and continue to beat until stiff, glossy peaks form.

Once the cupcakes are cool, cut a small hole in the center of each. Fill the hole with lemon curd. Pipe or spoon the meringue over the top of each cupcake, ensuring the curd is completely covered.

Using a kitchen torch, carefully toast the meringue until golden brown. Serve immediately or store as instructed.