Preheat your oven to 350°F (175°C). Line a baking sheet with parchment paper and set aside.
In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
In a large mixing bowl, cream the softened butter and granulated sugar using an electric mixer, until light and fluffy.
Beat in the egg, vanilla extract, lemon zest, and lemon juice until well combined.
Gradually add in the flour mixture, mixing until just combined.
In another small bowl, mix the raspberry puree with granulated sugar until smooth.
Take half of the cookie dough and dollop it onto the prepared baking sheet.
Use a small spoon to create divots in the dough, then drizzle the raspberry mixture over the top.
Take the remaining cookie dough and roll it into small balls. Press these on top of the raspberry mixture.
Using a toothpick or skewer, swirl together the raspberry mixture and cookie dough to create a marbled effect. Be careful not to overmix.
Bake for 10-12 minutes or until the edges are lightly golden. The centers may appear slightly soft but will firm up as they cool.
Allow the cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.