Preheat the oven to 180°C (350°F) and line 22 cupcake liners into two 12-hole cupcake pans.
Add the sugar and lemon zest to a small bowl and use the tips of your fingers to massage the lemon zest into the sugar.
Add the butter and lemon sugar mixture to a bowl of a stand mixer fitted with a paddle attachment. Beat at medium-high speed until creamed, about 3 minutes.
Add the eggs to the creamed butter and sugar mixture one at a time, be sure to scrape down the sides of the bowl with a rubber spatula between each addition.
Sift together the flour, baking powder, and salt into a large mixing bowl.
Add the sour cream and flour mixture to the cupcake batter by alternating between the two. Starting with the flour and ending with the sour cream. Once added, scrape the sides of the bowl and mix again briefly.
Use an ice cream scoop to fill the cupcake liners two-thirds of the way up the liner. Bake in a preheated oven for about 15 - 20 minutes or until a light golden brown and a cake tester inserted into the center of the cupcake comes out clean. Cool completely on a wire rack.
Lemon Drizzle Syrup
In a small saucepan set over medium heat add the lemon juice and sugar. Allow the sugar to dissolve and the syrup to thicken. Remove from the heat and cool to room temperature.
Vanilla Buttercream
Add the softened butter to a bowl of a stand mixer fitted with a whisk attachment. Beat at medium-high speed until the butter is light and fluffy.
Add the icing sugar to the whipped butter and beat again at medium speed until combined and light and fluffy. Add the frosting to a piping bag fitted with your chosen nozzle.
Use a pastry brush to brush the lemon syrup over the top of the cupcakes.Allow the syrup to seep into the cupcakes.
Pipe small swirls of frosting onto each cupcake. Decorate with lemon rind and curls of lemon zest. Serve and enjoy.