Lemon Meringue Cupcakes

Combine lemon juice, eggs, sugar, and lemon zest for lemon curd in a small saucepan over low heat. Cook, whisking constantly, until thick enough to coat the back of a spatula or spoon, about 10 minutes. Remove from the heat and strain through a sieve into a bowl. Stir in butter until melted; set aside.

Preheat the oven to 350 degrees F (175 degrees C). Line a 12-cup muffin tin with paper liners.

Sift flour, sugar, baking powder, and salt for cupcakes into a large bowl. Pour milk, oil, vanilla extract, and egg onto the dry mixture. Mix thoroughly with an electric mixer of by hand. Pour in hot water and mix to combine; batter will be thin. Spoon batter into the prepared muffin liners, filling about 3/4 full.

Bake in the preheated oven until tops spring back when lightly pressed, 15 to 18 minutes. Cool in the tin for 5 minutes. Transfer to a wire rack and let cool, about 20 minutes.

Core each cupcake using either a corer or a knife. Spoon in lemon curd.

Pour sugar and egg whites into a large bowl. Place the bowl over a saucepan or pot of simmering water. Whisk constantly until sugar is dissolved and egg whites are warm, to between 120 and 140 degrees F (49 to 60 degrees C) on a thermometer, 4 to 6 minutes. Remove from the heat.

Mix in lemon juice and whip at high speed until stiff peaks form. Pipe meringue onto the cupcakes.

Set an oven rack about 10 inches from the heat source and preheat the oven's broiler.

Place cupcakes under the preheated broiler until meringue has browned, about 2 minutes.