Preheat the oven to 350 degrees fahrenheit.
Prep a cupcake pan with cupcake liners.
Start by making the crust. In a bowl, mix together the butter, brown sugar, white sugar, and salt until combined.
Then add the flour and mix until a crumbly crust is formed.
Take about tablespoon of the crust and add to each cupcake liner, flattening afterwards with the spoon.
Bake in the oven for 10 minutes.
While that is baking, start making the cupcake filling.
In a bowl, whisk together the sugar, eggs, vanilla extract and lemon juice.
Add 1 cup of flour and the baking powder to the wet mixture and mix until combined.
Fill each cupcake liners 1/2 the way full with cupcake batter and place in the oven for another 22 minutes.
Remove from the oven and allow to cool for 15 minutes before piping on some lemon buttercream frosting and topping with lemon curd.