Prepare the baking pan and the oven: Cut a strip of  parchment paper measuring 16 ½ inches long and wide enough to line the bottom of a 9x9 baking pan. Place the parchment in the pan leaving 2 inches of overhang. This makes it easier to lift the cake out of the pan later. Preheat your oven to 350 degrees.

 Make the crumb topping: Combine the flour, brown sugar, melted butter and lemon zest in a small bowl. Cover and set aside.

Combine the dry ingredients: Using a medium sized bowl, combine the flour, baking powder, baking soda, and salt. Whisk to combine. Set aside.

Combine the wet ingredients: Pour the yogurt into a large bowl, add the egg and whisk to combine. Add the milk, melted butter, oil, sugar, vanilla, lemon zest and juice, whisk until well combined. It should be a smooth consistency.

Combine the wet into the dry ingredients: Add the dry ingredients to the wet in batches. Add ⅓ of the flour mixture to the wet and fold using a flexible spatula. When most of the flour has been incorporated, add half of the remaining flour mixture, fold again, then add the remaining flour and fold until there is no more dry flour. Your batter should be light and fluffy.

Assemble - Spoon half the batter into the pan and spread on the bottom of the pan, and 

sprinkle half of the crumble mixture over the batter. 

Top the crumble layer with the blueberries. If you are using frozen blueberries don’t thaw them. Keep them frozen until you are ready to layer them in your batter.

Spoon the remaining batter over the blueberries and spread evenly, then sprinkle the remaining crumble over the top of the batter. 

Bake the cake in the middle of the oven for 25-30 minutes or until a toothpick inserted comes out clean and the cake springs back when you touch the top.

Make the cream topping: While the cake is baking in the oven, use a small bowl to whisk all of the cream topping ingredients together until  smooth and creamy. (Depending on the temperature of your kitchen, you may need to microwave your cream cheese for a few seconds to soften before adding the remaining ingredients.) Transfer topping to a piping bag or zip bag and set aside.

Cool: Remove from the oven and allow to cool. Once the cake has cooled, use the parchment paper to lift the cake out of the pan and place on a cutting board or other flat surface.

 Top cake with cream topping: Spread or drizzle the cream topping over the top of the cake using a piping bag or a zip bag with a corner of the bag cut.

Serve:Slice the cake into 16 squares and serve at room temperature or slightly warm.