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

Cream together ½ cup of room temperature unsalted butter, ⅓ cup of cold-pressed oil, and 1 cup of granulated sugar until light and fluffy, about 2–3 minutes. Add one egg and lemon zest; mix until combined.

In another bowl, whisk together 2 cups of all-purpose flour, 1 teaspoon of baking powder, and a pinch of salt. Gradually add to the wet mixture, stirring until just combined.

Gently fold in ⅓ cup of blueberry jam into the cookie dough, aiming for a marbled effect.

Scoop the dough onto the prepared baking sheet, spacing each scoop about 2 inches apart.

Bake for about 10-12 minutes or until set but still soft in the center.

Cool on the baking sheet for about 5 minutes, then transfer to a wire rack to cool completely.