Add the sugar and lemon zest to the bowl of a food processor and pulse until the mixture is pale yellow and the zest is fully incorporated into the sugar.

Whisk together the flour, baking soda, baking powder, and salt in a large bowl and set aside.

In a separate bowl, whisk the eggs, milk, melted butter, lemon juice, sour cream, and lemon sugar until well combined.

Add the wet ingredients into the dry ingredient mixture and fold gently until just combined.

Fill each well of a lined muffin tin ¾ of the way full.

Bake for 5 minutes at 375F and then reduce the temperature to 350F and bake for another 10-12 minutes or until a toothpick inserted into the center comes out clean.

Allow the cupcakes to cool for 10 minutes in the pan before transferring to a rack to cool completely.

While the cupcakes cool, make the buttercream.

In the bowl of a stand mixer, use the whisk attachment to beat the butter and cream cheese together until well combined and smooth.

Add the powdered sugar 1 cup at a time, beating well between each addition.

Whisk in the vanilla and elderflower syrup.

Top each cupcake with a generous 3 tbsp of frosting and use an offset spatula to smooth across the top and edges.

Add on the rose petals and sprinkles or decorate as desired.