Get started by making your vibrant raspberry swirl! In a small bowl, gently mash your fresh (or thawed frozen) raspberries with the sugar and optional lemon juice until you have a beautiful, thick puree. Set this lovely mixture aside.
Next, let's prepare the cookie dough. In one bowl, whisk together the flour, baking soda, and salt. In a separate, larger bowl, beat the softened butter and granulated sugar until they're wonderfully light and fluffy. Stir in the egg and vanilla extract until everything is perfectly combined. Now, gradually add your dry ingredients to the wet mixture, mixing just until a soft dough forms.
Time for the gorgeous swirl! Carefully fold the raspberry puree into your cookie dough using a spatula. Remember not to overmix – we want those lovely pink streaks for a beautiful marbled effect, not a uniform color.
Preheat your oven to a cozy 350°F (175°C) and line your baking sheets with parchment paper. Scoop tablespoon-sized portions of dough and place them a couple of inches apart on the sheets. Bake for 10-12 minutes, or until the edges are just lightly golden. They'll be soft and perfect!
Once baked, let your delightful cookies cool on the baking sheet for about 5 minutes. This helps them set up beautifully before you transfer them to a wire rack to cool completely. Enjoy them warm or cooled – either way, they're a treat!