Preheat your oven to 350°F (175°C). Line two baking sheets with parchment paper or silicone mats.
In a large mixing bowl (or using a stand mixer), combine the softened butter and granulated sugar. Beat them together until the mixture is light, fluffy, and looks like a creamy dream.
Stir in the vanilla extract, the large egg, and the vibrant lemon zest and juice. Mix until everything is beautifully combined, scraping down the sides of the bowl to ensure no ingredient is left behind.
Gently fold in the salt, baking powder, baking soda, and all-purpose flour. Mix just until the flour disappears and everything comes together into a soft dough. Be careful not to overmix!
Quickly add the coarsely chopped frozen raspberries. Mix them in just enough to distribute throughout the dough, creating lovely pink swirls without overworking the berries. (Keeping them frozen helps achieve this beautiful marbled effect!)
Using a cookie scoop (or two spoons for an easy drop-cookie style), place tablespoon-sized portions of dough onto your prepared baking sheets. Don't worry if the dough is a bit sticky – that's normal!
Pop your cookie sheets into the preheated oven. Bake for about 14-16 minutes, or until the edges are just starting to turn golden and the tops are no longer glossy. (If baking in batches, store any unbaked dough in the fridge to keep the raspberries firm.)
Let your delicious cookies cool on the baking sheets for about 10 minutes before gently transferring them to a wire rack to cool completely. They firm up beautifully as they cool!