• Preheat oven to 350°F.
• Line a 9*9-inch pan with parchment paper or spray it with baking spray.

For the crumb topping:

• in a medium bowl, combine the melted butter and sugar. Add the flour. Using a fork, mix until crumbly. Set aside.
• In another medium bowl, whisk together the flour, baking powder, and salt.
• Add lemon zest and sugar to a large bowl. Press together with a silicone spatula to release the lemon oils.
• Add in eggs and vanilla. Whisk together for one minute until frothy and pale.
• Add in vegetable oil and sour cream. Whisk to combine.
• Add the flour mixture. Mix just until combined.
• In a medium bowl, beat the cream cheese with sugar, egg and vanilla until smooth.
• Pour the batter into the prepared pan. Spread the cream cheese mixture over the cake batter. Top with an even layer of blueberries and crumb topping.
• Bake for 45-50 minutes, or until a toothpick inserted in the center of the cake comes out clean. Remove from oven and allow to cool for 10-15 minutes before removing from pan. Let cool completely on a wire rack.

For the icing:

• whisk the ingredients together until smooth. Drizzle over the cooled cake. Sprinkle the cake with lemon zest.
• Enjoy!