Step 1: Preheat and Prep
Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper and set aside.

In a large bowl, combine the granulated sugar and lemon zest. Use your fingers to rub the zest into the sugar until it becomes fragrant and slightly moist.

Step 2: Cream the Butter and Sugars
Add the softened butter and brown sugar to the bowl. Beat on medium-high speed for about 3–4 minutes until light and fluffy.

Add the egg yolk, lemon juice, and vanilla extract. Beat until fully incorporated.

Step 3: Mix the Dry Ingredients
Add the salt, baking powder, baking soda, and flour to the bowl. Mix on low speed or stir by hand until just combined. Avoid overmixing.

Step 4: Fold in the Raspberries
Chop the frozen raspberries into small pieces. Fold them gently into the dough using a spatula. Don’t overmix—the dough should be marbled with pink streaks, not fully pink.

Step 5: Scoop and Sprinkle
Use a 3-tablespoon cookie scoop to portion out the dough. Place 5 to 6 dough balls per tray to allow space for spreading.

Sprinkle a small pinch of flaked salt on top of each cookie if using.

Step 6: Bake and Cool
Bake for 12 to 15 minutes, or until the edges are lightly golden and the centers look just set.

Remove from the oven and let them sit on the tray for 5 minutes before transferring to a wire rack to cool completely.