Preheat oven to 350 degrees F. Grease a 9-inch springform pan with butter. An 8x8 square pan would also work, but make sure to line it with parchment paper with overhang.
Make the streusel: In a medium bowl, combine the dry ingredients. Add the cold butter cubes, and using a pastry blender or a fork, cut the butter into the mixture until you get small pea-size crumbles. Place prepared topping in refrigerator while you make the cake batter.
Combine flour, baking powder, baking soda, and salt in a medium bowl. Set aside.
In a separate bowl, cream 6 tablespoons softened butter, sugar, and lemon zest using an electric or stand mixer. Add the eggs, one by one, and beat until smooth. With a hand whisk, mix in Greek yogurt, vanilla extract, and lemon juice until well combined.
Using a rubber spatula, fold in the dry ingredients to the mixture, and mix until just combined.
Gently fold in the blueberries to the batter. Try not to burst them.
Pour the batter into the prepared pan. Even out with the rubber spatula. Top with the streusel topping. Bake for about 40-45 minutes, until a toothpick or cake tester inserted in the middle comes out clean. Let cool for 20 minutes.
Make the lemon glaze: while cake is cooling, make the glaze. Whisk together the powdered sugar with lemon juice until a thin (but not watery) glaze forms.
Once the cake has cooled to room temperature, drizzle with the lemon glaze. Cut into slices and serve. Enjoy!