Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan.
In a medium bowl, mix the flour, sugar, baking powder, and salt.
In another bowl, beat the softened butter, cream cheese, egg, and vanilla extract until smooth.
Add the dry ingredients to the wet mixture and stir until well combined.
Gently fold in the blueberries.
Pour the batter into the prepared cake pan.
In a small bowl, combine the brown sugar, flour, and cinnamon for the crumb topping. Sprinkle over the cake batter.
Bake for 30-35 minutes or until a toothpick inserted into the center comes out clean.
Let the cake cool before serving.
