Preheat oven to 350 degrees F.
First, make the streusel topping. In a medium bowl, combine the flour, sugar, and melted butter. Mix with a fork or your fingers until well combined. Set aside.
In a large bowl, combine the sugar and lemon zest. Rub together with your fingers until fragrant. Add the flour, baking powder and salt. Whisk together and set aside.
In a medium bowl, whisk together the ricotta cheese, eggs, lemon juice, and vanilla. Gradually add in the melted butter, whisking until combined and smooth.
Add the ricotta mixture to the dry ingredients and stir with a spatula until just combined. Don’t over mix. Gently fold in the blueberries, being careful not to over mix or the batter will turn purple.
Grease a 9-inch springform pan generously with nonstick cooking spray. Scrape the batter evenly into the pan and sprinkle evenly with the streusel.
Bake for 45 to 55 minutes or until a toothpick inserted into the center of the cake comes out clean. Remove the pan from the oven and place on a cooling rack. Let the cake cool in the pan for 30 minutes, then carefully remove the sides of the springform pan.
In a medium bowl, whisk together the confectioner’s sugar and lemon juice. I always start with 2 tablespoons. If the glaze is too thick, you can add a little more lemon juice until desire consistency is reached.
Drizzle the lemon glaze over the cooled cake. Cut the cake into slices and serve!