Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, combine the granulated sugar and lemon zest, rubbing them together until fragrant.

Add the softened butter and brown sugar, then beat on medium speed for 3-4 minutes until light and fluffy.

Mix in the egg yolk, vanilla extract, and lemon juice until fully combined.

Gradually add the salt, baking powder, baking soda, and flour, mixing just until no flour remains.

Gently fold in the chopped frozen raspberries using a spatula.

Drop dough onto the prepared baking sheets, spacing them about 2 inches apart; sprinkle flaked salt on top if desired.

Bake for 12-15 minutes, or until the edges are lightly golden and the centers are slightly soft.

Let the cookies cool on the sheets for about 5 minutes before transferring them to a wire rack.