01 - Preheat the oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - Whisk together flour, baking powder, baking soda, and salt in a bowl.
03 - In a large bowl, cream the butter and sugar until light and fluffy. Beat in eggs one at a time, then stir in vanilla and lemon zest.
04 - Add the dry ingredients in three parts, alternating with the milk. Mix until just combined.
05 - Divide batter evenly among cupcake liners. Bake 18–22 minutes, or until a toothpick comes out clean. Cool completely.
06 - In a heatproof bowl, whisk eggs, yolks, sugar, lemon juice, and zest. Set over a saucepan of simmering water and whisk until thickened, about 8–10 minutes. Remove from heat, whisk in butter until smooth. Cool completely.
07 - In a clean bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar, beating until stiff peaks form. Beat in vanilla.
08 - Use a knife or apple corer to remove a small section from the center of each cupcake. Fill with lemon curd.
09 - Pipe or spoon meringue over each cupcake. Use a kitchen torch to toast the meringue until golden, or place under broiler for 1–2 minutes, watching closely.
10 - Serve immediately or refrigerate until ready to serve.