Preheat the oven to 350°F (175°C). Grease and flour a 9-inch round cake pan.

In a mixing bowl, cream together the sugar and softened butter until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the milk.

In another bowl, whisk together the flour, baking powder, and salt. Gradually add to the wet ingredients until just combined.

Gently fold in the blueberries.

In a separate bowl, combine the flour, sugar, melted butter, and cinnamon. Mix until crumbly.

Pour the cake batter into the prepared pan and sprinkle the crumb topping evenly over the batter.

Bake in the preheated oven for 40-45 minutes, or until a toothpick inserted into the center comes out clean.

Allow to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.