Mash fresh raspberries in a bowl with a tablespoon of sugar until thick, about 3-5 minutes.

Whisk together flour, baking soda, and salt in a bowl. Set aside.

Beat softened butter and sugar until light and fluffy, about 3-4 minutes.

Add egg and vanilla to the creamed mixture and mix until combined.

Slowly add dry ingredients into the butter mixture, stirring until just combined.

Fold in raspberry puree gently to create a marbled effect.

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

Scoop cookie dough onto prepared sheets, spacing them 2 inches apart.

Bake for 10-12 minutes, until edges are lightly golden and centers look underbaked.

Cool cookies on the baking sheet for 5 minutes before transferring to a wire rack.