Preheat oven to 350 degrees. Spray a 9×9″ square baking pan with non stick spray. Line it with parchment paper, and spray the parchment again. Set aside.

To make the crumble topping, combine all the ingredients into a bowl, and using your hands, squeeze it all together until a course crumble forms. To save time, you can also do this in a stand mixer, mixing the ingredients with a paddle attachment on low speed until a crumble just starts to form. Remove and use your hands to press it all together and them crumble it into large pieces. Place it in the fridge to chill until ready to use.

In the same stand mixer bowl, beat together the sugar and eggs until light and fluffy. With the mixer on low, add in the melted and cooled butter, sourdough starter, sour cream, vanilla and almond extract. Mix until just combined. Scrape the bowl once, to ensure that nothing is lingering at the bottom of the mixing bowl.

In a large bowl, whisk together the flour, baking powder, baking soda, and additional cinnamon. Turn the mixer on low, and add in the dry ingredients a 1/2 cup at a time. Scrape the bowl once to ensure nothing is sticking to the bottom of the bowl. Do not overmix. Pour the dough into the prepared pan and smooth it out to the edges and corners. It will be sticky, so spray a spatula with non stick spray to help spread it out without sticking.

Place one cup of the blueberries on top of the batter, and lightly press them into the dough so they stick. Sprinkle half of the chilled crumble on top of the blueberries. Repeat with the other cup of blueberries, and last half of the crumble.

Bake for 40 minutes, checking it at 35 minutes. It may take up to 45 minutes to bake through depending on your oven. When a toothpick comes out clean, it is done. Remove and place on a wire cooling rack. Slice and serve when cooled completely.