01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a medium bowl, whisk together flour, oats, baking soda, baking powder, and salt until well blended.
03 - In a large bowl, beat softened butter, granulated sugar, and brown sugar until light and fluffy, about 2–3 minutes.
04 - Beat in egg, vanilla extract, lemon zest, and lemon juice until fully incorporated and smooth.
05 - Gradually add dry ingredients to wet mixture, mixing just until combined. Do not overmix.
06 - Gently fold in raisins and raspberries. Raspberries will break down slightly for a marbled effect.
07 - Drop heaping tablespoons of dough onto prepared baking sheets, spacing about 2 inches apart.
08 - Bake for 11–13 minutes until edges are golden and centers are just set.
09 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.