Prepare the raspberry frosting first. In a mixing bowl, beat the softened butter with the pinch of salt, vanilla essence, and confectioners’ sugar until the texture is smooth and creamy.
Add the powdered raspberries along with the milk, then mix until fully incorporated and the frosting reaches the consistency you prefer. Set it aside.
Preheat the oven to 350°F (175°C). Line two greased baking sheets with parchment paper so the cookies bake evenly and release easily.
For the cookie dough, place the butter, fine sea salt, vanilla essence, lemon zest, granulated sugar, and confectioners’ sugar in the bowl of a stand mixer. Beat on medium speed for 4 to 5 minutes, until the mixture becomes pale and fluffy.
Add the egg and continue mixing for 2 more minutes.
Gradually incorporate the flour and baking soda, beating just until the dough comes together into a uniform ball.
Using about 3 tablespoons of dough for each cookie, portion the dough onto the prepared baking sheets to form large cookies.
Roll each portion between your hands to create smooth balls. Flatten them with the back of a floured 1/4-cup measuring cup, pressing gently in the center.
Bake for 12 minutes, or until the bottoms are just beginning to turn golden.
Remove the cookies from the oven and allow them to cool completely before frosting.
Once cooled, place about 1 tablespoon of raspberry frosting on each cookie and spread it evenly over the surface.
Finish with any decorative toppings you like, then serve.