In a medium bowl, combine all-purpose flour, granulated sugar, dark brown sugar, cinnamon, and softened butter. Mix until the mixture resembles coarse crumbs, about 2-3 minutes. Set aside.

Preheat the oven to 175ºC (350ºF). Prepare a 9-inch springform pan by buttering and lining the bottom with parchment paper.

In a large mixing bowl, beat butter and granulated sugar together until light and fluffy, about 3-4 minutes. Add eggs one at a time, mixing well after each addition. Gradually incorporate half of the dry ingredients.

Add lemon zest, sour cream, vegetable oil, and vanilla extract to the batter. Mix until just combined, then fold in the remaining dry ingredients until no dry flour is visible.

Toss the blueberries with cornstarch. Gently fold half of the blueberries into the batter. Pour the batter into the prepared pan, smoothing the top, and sprinkle remaining blueberries and crumble topping on top.

Bake in the preheated oven for 45-50 minutes. Check for doneness with a toothpick. Allow to cool in the pan for about 10 minutes before transferring to a wire rack.

Whisk together powdered sugar, lemon juice, vanilla extract, and sour cream in a small bowl until smooth. This is the lemon glaze.

Once the cake is cool, drizzle the lemon glaze over the top. Allow the glaze to set before slicing.