Adjust an oven rack to the middle position and heat to 350 degrees F. Grease and flour a 9 x 13-inch baking pan.
Whisk 2 cups of the flour, the baking powder, and salt together in a medium bowl. With an electric mixer, beat the butter and sugars on medium-high speed until fluffy, about 2 minutes.
Add the eggs, one at a time, beating until just incorporated. Reduce the speed to medium and beat in one-third of the flour mixture until incorporated; beat in 1/2 cup of the milk. Beat in half of the remaining flour mixture, then the remaining 1/2 cup milk and finally the remaining flour mixture.
Toss the blueberries in a small bowl with the remaining 1 teaspoon flour. Using a rubber spatula, gently fold the blueberries into the batter. Spread the batter into the prepared pan.
For the topping, scatter the blueberries over the top of the batter.
Stir the sugar and cinnamon together in a small bowl and sprinkle over the batter. Bake until a toothpick inserted in the center of the cake comes out clean, 45 to 50 minutes. Cool in the pan for 20 minutes, then turn out and place on a serving platter (topping side up). Serve warm or at room temperature. The cake can be stored in an airtight container at room temperature for up to 3 days.