01 - Preheat oven to 350°F. Line a 12-cup muffin tin with cupcake liners.
02 - In a bowl, whisk together flour, baking powder, baking soda, and salt.
03 - In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs one at a time, then add lemon zest and juice.
04 - Add flour mixture in three parts, alternating with milk. Mix until just combined.
05 - Divide batter evenly among cupcake liners. Bake for 18-20 minutes, or until a toothpick comes out clean. Cool completely on a wire rack.
06 - In a heatproof bowl, whisk eggs, sugar, lemon juice, and zest. Place bowl over a saucepan of simmering water. Whisk constantly until thickened, about 8 minutes. Remove from heat and stir in butter until smooth. Cool completely.
07 - Using a small knife or apple corer, remove the center of each cupcake. Fill each cavity with lemon curd.
08 - In a clean bowl, beat egg whites and cream of tartar until soft peaks form. Gradually add sugar and continue beating until stiff, glossy peaks form. Beat in vanilla.
09 - Pipe or spoon meringue onto cupcakes. Toast meringue under a broiler for 1-2 minutes or use a kitchen torch until golden.
10 - Serve immediately or refrigerate for up to 2 days.