Line a 12-cup muffin tin with cupcake liners and preheat your oven to 180°C (350°F).

Combine the finely grated lemon zest with granulated sugar in a bowl, and rub them together until it resembles moist sand.

In a mixer bowl, whisk together the cake flour, lemon-infused sugar, chopped pistachios, baking powder, and fine sea salt.

Add cubed unsalted butter into the dry ingredients and mix on low speed for about 3 minutes until coarse and crumbly.

In a separate bowl, whisk together sour cream, milk, vegetable oil, egg, vanilla extract, and lemon juice.

Pour the wet mixture into the dry ingredients and mix until just combined.

Divide the batter among the muffin cups, filling each about three-quarters full. Bake for 15-20 minutes or until a toothpick comes out with a few moist crumbs. Let cool for 5 minutes before transferring to a wire rack.

In a saucepan, cook raspberries, sugar, and lemon juice over medium heat, mashing and stirring until bubbling and bright red (about 10-12 minutes). Whisk cornstarch with water, stir it into the mixture, and cook for an additional 1-2 minutes until thickened. Allow to cool completely.

In a stand mixer, cream the unsalted butter until smooth. Gradually add powdered sugar until fully incorporated, then mix in heavy cream, lemon juice, and grated lemon zest.

Core the center of each cooled cupcake and spoon in the raspberry filling. Pipe the lemon buttercream around the filled center and top with more raspberry filling.

Finish by garnishing with chopped pistachios and fresh raspberries.