1. Preheat your oven to 350 degrees F and line cupcake tins with paper liners or spray them with non-stick cooking spray. Your kitchen will soon fill with the wonderful scent of baking cupcakes.
2. In a large bowl, sift together the cake flour, baking powder, and kosher salt. Sifting ensures the dry ingredients are well combined and helps create a lighter texture in your cupcakes.
3. In another medium bowl, whisk together the buttermilk and egg whites. Make sure they are at room temperature; this helps them blend more easily into the batter.
4. Now, in the bowl of your mixer, combine the sugar and lemon zest. Rub them together with your fingers until the sugar is moist and fragrant. This step really enhances the lemon flavor in your cupcakes!
5. Add the butter to the sugar mixture and beat at medium speed until the mixture is light and fluffy, about 3 minutes. This will give your cupcakes a lovely airy texture.
6. Beat in the vanilla extract next, then gradually add one third of the flour mixture, beating on medium speed. This gradual addition helps prevent lumps in your batter.
7. Now, add half of the milk-egg mixture, continuing to beat. Then mix in half of the remaining dry ingredients until everything is well incorporated.
8. Add the rest of the milk and eggs, mixing until the batter is thoroughly combined. Finally, add the last of the dry ingredients, and give the batter a good 2-minute beating to aerate it.
9. Using a large scoop (about 3 tablespoons), distribute the batter evenly among 24 muffin wells, filling each well about two-thirds full. This will give your cupcakes enough room to rise.
10. Bake for 18 to 22 minutes, or until the cupcakes feel springy to the touch and a toothpick inserted in the center comes out clean. Once baked, cool them on a wire rack.
11. Once the cupcakes have cooled, hollow out a small circle in the center of each one using an apple corer for a neat finish. Spoon or pipe in a dollop of lemon curd, allowing the tangy goodness to be a surprise inside!
12. Now, to prepare the meringue, combine 1 1/2 cups sugar with water and corn syrup in a small saucepan. Clip a candy thermometer to the side of the pan and bring the mixture to a boil over medium heat, stirring occasionally until the sugar dissolves completely.
13. Continue boiling without stirring until the syrup reaches 230 degrees F. This stage is crucial for achieving the right consistency in your meringue.
14. Meanwhile, in the bowl of a stand mixer fitted with the whisk attachment, whisk the additional egg whites on medium-high speed until soft peaks form. With the mixer running, gradually add the remaining 2 tablespoons of sugar until combined.
15. As soon as the sugar syrup reaches 230 degrees, remove it from the heat. With the mixer on medium-low speed, pour the syrup down the side of the bowl in a slow, steady stream.
16. Raise the mixer speed to medium-high and whisk until the mixture is completely cool (you can test this by touching the bottom of the bowl) and stiff peaks form, about 7 minutes. Use the meringue immediately to frost your cooled cupcakes.
17. For the final touch, use a kitchen torch to lightly brown the meringue frosting. This adds an irresistible toasted flavor that complements the tangy lemon filling perfectly!
