• Make crumble topping: In a small bowl, add brown sugar, flour, melted butter, cinnamon, and salt.
  ¾ cup brown sugar, ¾ cup all-purpose flour, ½ cup melted unsalted butter, 1 teaspoon ground cinnamon, ¼ teaspoon salt
• Mix crumble with a fork until well incorporated. Set aside. (As the butter mixture cools it will thicken and become more crumbly.)
• In a large bowl, whisk together the flour, baking powder, baking soda, and salt and set aside.
  2 cups all-purpose flour, 1 teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
• In a separate mixing bowl, cream butter and sugar with an electric hand mixer for approximately 1 minute until light and fluffy.
  ½ cup unsalted butter, ¾ cup granulated sugar
• Add the eggs, sour cream, milk, and vanilla extract. Mix for 1 minute until well incorporated.
  2 large eggs, 1 cup sour cream, ¼ cup 2% milk, 1 teaspoon vanilla extract
• Stir wet ingredients into the dry mixture. Stir with a spatula or mixing spoon until combined, the batter will be thick.
  
• In a small bowl, add blueberries and flour.
  1 ½ cups fresh blueberries, 2 tablespoons all-purpose flour
• Toss gently until the blueberries are coated evenly with the flour.
• Gently fold the blueberries into the cake batter. (To avoid adding extra flour to the batter, add the blueberries to the batter with a slotted spoon rather than dumping them in.)
• Add batter to the greased pan and spread out evenly.
• Break up crumble with your hands and sprinkle topping over batter.
• Bake for 50-55 minutes or until a toothpick inserted into the center comes out clean. Let the cake cool in the pan for about 10 minutes before removing from the springform pan.
  

Lemon Glaze (optional)

• Let coffee cake cool completely before adding glaze. In a small bowl, whisk together powdered sugar and milk until smooth. Add more or less milk depending on desired thickness.
  ⅔ cup powdered sugar, 1 tablespoon milk, 1 tablespoon lemon juice