Preheat your oven to 375°F (190°C). Prepare your baking equipment, including cupcake liners and a muffin tin.

In a large mixing bowl, combine unsalted butter and granulated sugar, beating until light and fluffy, about 3-5 minutes. Add the room temperature eggs one at a time, mixing well after each, followed by lemon juice, baking powder, and salt.

Sift all-purpose flour into the mixture and fold gently until combined, being careful not to overmix.

Fill cupcake liners in the muffin tin with batter until about two-thirds full.

Bake for 15-16 minutes, until cupcakes spring back to the touch. Let cool in the pan for 5-8 minutes before transferring to a wire rack.

Beat egg whites with a pinch of salt until foamy. Gradually add granulated sugar, beating until stiff peaks form, about 5-7 minutes.

Hollow out a cavity in the center of each cooled cupcake, making enough space to fill with lemon pie filling.

Spoon lemon pie filling into the hollowed portions of each cupcake.

Spoon prepared meringue over filled cupcakes, creating peaks. Toast the meringue in the oven or with a kitchen torch until golden brown, about 2-3 minutes.

Cool at room temperature for 10 minutes, then refrigerate for at least 1 hour before serving.