Preheat oven to 350°F (175°C) and grease a 9-inch round pan.
In a bowl, cream sugar and butter until fluffy. Add eggs and vanilla.
Mix in flour, baking powder, and salt, alternating with milk. Pour batter into prepared pan.
For the filling, beat cream cheese, sugar, egg, and vanilla. Spread over the batter.
Sprinkle blueberries evenly over the cream cheese mixture.
For the streusel, combine butter, sugar, flour, and cinnamon until crumbly. Sprinkle over the top.
Bake for 45-50 minutes or until a toothpick inserted in the center comes out clean.
Cool before serving.