In a medium bowl, whisk together all of the dry ingredients.

Pour in the melted butter and mix to combine. It should be evenly moistened with a mix of large and small clumps.

Place in the refrigerator while we make the batter.

Preheat the oven to 350F and grease and line the bottom of a 9″ springform pan.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large mixing bowl using a hand or stand mixer with the paddle attachment, mix together the butter and sugar until light and fluffy.

Then mix in the egg and extracts, followed by the sour cream.

Before mixing in the dry ingredients, first prep the blueberries.

Place the clean blueberries in a bowl and toss with the zest. Then toss with the cornstarch.

Now back to the batter. Mix in the dry ingredients and just before it’s all combined, add in half of the blueberries.

Switch to a rubber spatula and mix in the berries by hand, careful not to break them. The batter will also be VERY thick.

Spread the batter in the bottom of the prepared pan and top with an even layer of the remaining blueberries.

Top with a layer of the chilled crumble and bake for 45-50 minutes, or until a toothpick in the center comes out clean with a few moist crumbs.

Allow the cake to cool for about 1 hour at room temperature.

For the icing, whisk together all of the ingredients and drizzle over the cooled cake.

Now slice and enjoy!