Beat butter, cream cheese, and sugar on medium speed until light and fluffy, about 2 to 3 minutes. Mix in egg and vanilla until smooth.

Whisk flour, baking powder, salt, and lemon zest in a small bowl. Add to butter mixture on low speed until a few flour streaks remain, then stir in the ½ cup graham cracker crumbs until just combined.

Gently fold in blueberries with a spatula. Cover and chill dough for at least 30 minutes.

Preheat oven to 350°F (175°C). Scoop dough by rounded 1.5 tablespoons, roll each ball in extra graham cracker crumbs, and place 2 inches apart on parchment-lined baking sheets. Bake 12 to 14 minutes, until edges are lightly golden and tops look set but soft.

Cool cookies on the sheet for 5 minutes, then transfer to a wire rack. Serve warm or at room temperature.