Prepare the Pan: Preheat the oven to 350°F. Brush the bottom and sides of a 9-inch springform pan evenly with softened butter, then line the bottom with a round of parchment paper.
Prepare the Crumb Topping: Combine the flour, granulated sugar, cinnamon, and salt in a small bowl. Add the melted butter and vanilla, then toss with a fork until the mixture forms loose, crumbly pieces. Place the topping in the freezer until it is needed.
Combine Dry Ingredients: Whisk the flour, aluminum-free baking powder, baking soda, and salt together in a medium bowl until evenly combined.
Cream Butter and Sugar: Place the room-temperature butter and granulated sugar in a large mixer bowl. Beat on medium speed until the mixture becomes light and fluffy, then mix in the vanilla extract.
Add Eggs: Reduce the mixer speed to low and add the eggs one at a time, followed by the egg yolk, incorporating each before adding the next.
Combine Dairy: Stir the room-temperature buttermilk and sour cream together in a small bowl.
Finish the Batter: Add the dry ingredients to the butter mixture in three additions, alternating with the buttermilk mixture. Begin and end with the flour mixture, mixing only until the ingredients are incorporated.
Fill the Pan: Scrape the batter into the prepared springform pan and smooth the surface evenly with an offset spatula. Tap the pan sharply to release air bubbles.
Add Blueberry Preserves: Spoon the blueberry preserves over the batter in small portions. Gently swirl the preserves into the batter using a toothpick or wooden skewer, taking care not to overmix.
Add Blueberries: Scatter the blueberries evenly over the batter, then cover the surface with the chilled crumb topping.
Bake the Cake: Bake at 350°F for 65 to 70 minutes, until the edges are golden, the cake springs back when gently touched, and a toothpick inserted into the center comes out clean or with a few crumbs attached.
Cool the Cake: Transfer the baked cake to a wire rack and let it cool for 30 minutes before carefully removing the sides of the springform pan. Allow the cake to cool completely.
Prepare the Glaze: Whisk the melted butter, salt, vanilla extract, powdered sugar, and milk together in a small bowl until smooth.
Glaze the Cake: Drizzle the glaze over the completely cooled crumb cake and allow it to set before serving.
Store the Cake: Keep the crumb cake at room temperature overnight, or wrap it well and refrigerate for up to 3 days. Reheat it in a warm 300°F oven before serving.
