I preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper for easy cleanup.

In a bowl, I whisk 1 ½ cups flour, ½ tsp baking powder, and ¼ tsp salt. I set this aside for the base of Blueberry Swirl Sugar Cookies.

In a large bowl, I beat ½ cup softened butter and ½ cup granulated sugar with an electric mixer for 2–3 minutes until light and fluffy.

I mix in 1 egg and 1 tsp vanilla extract, beating until fully combined.

I gradually add the dry ingredients to the wet, mixing until a soft dough forms. I use my hands to bring it together if needed, then chill the dough in the refrigerator for 15 minutes to make it easier to roll.

On a lightly floured surface, I roll the dough into a ¼-inch thick rectangle. I spread ½ cup blueberry jam evenly over the dough, leaving a thin border. If the jam is thick, I warm it slightly for easier spreading.

I roll the dough into a log from the long side, then slice into ½-inch thick rounds. I place the slices 2 inches apart on the baking sheet.

I bake for 12–15 minutes until the edges are lightly golden. I cool the cookies on the sheet for 5 minutes, then transfer to a wire rack to cool completely.

I serve these cookies at room temperature, enjoying their fruity swirls with a refreshing drink.