Preheat oven to 350°F (175°C). Line baking sheet with parchment.

Cream butter, cream cheese, and sugar until light. Beat in egg and vanilla, then mashed bananas.

Whisk flour, baking soda, salt, and cinnamon; fold into wet mixture until just combined.

Drop tablespoons of dough onto sheet. Swirl a small additional dollop of cream cheese on top and use a toothpick to create a marbled look.

Bake 10–12 minutes until edges set and tops are lightly golden. Cool 5 minutes on sheet, then transfer to rack.