• Preheat oven to 180°C (350°F).
• Line muffin tin with cupcake liners.
• In a bowl, cream butter and sugar until light and fluffy.
• Beat in eggs one at a time.
• Stir in lemon zest and lemon extract.
• Alternately add flour and milk, mixing until just combined.
• Fill cupcake liners 2/3 full.
• Bake for 18-20 minutes, or until a toothpick inserted comes out clean.
• Let cupcakes cool completely.

For the Lemon Curd Filling:

• In a saucepan, combine lemon juice, sugar, and egg yolks.
• Cook over medium-low heat, stirring constantly, until thickened.
• Stir in butter and cook until melted.
• Let cool completely.
• Core the center of each cooled cupcake and fill with lemon curd.

For the Meringue Topping:

• In a heatproof bowl set over a saucepan of simmering water, combine egg whites, sugar, and cream of tartar.
• Whisk until sugar dissolves and mixture is warm.
• Remove from heat and beat with an electric mixer until stiff, glossy peaks form.
• Pipe or spoon meringue onto each cupcake.
• Lightly torch the meringue with a kitchen torch, or broil for 1-2 minutes until golden.
• Serve immediately.