Preheat the oven to 350 degrees F (175 degrees C). Coat a 9-inch springform pan with cooking spray.

Whisk together 1 cup sorghum flour, brown rice flour, potato starch, tapioca starch, baking powder, xanthan gum, baking soda, and kosher salt in a large bowl; make a well in the center.

Whisk together buttermilk, sugar, canola oil, eggs, egg whites, and lemon zest in a medium bowl. Pour buttermilk mixture into the well of the flour mixture and stir to combine batter; do not overmix.

Toss blueberries with 1 tablespoon sorghum flour in a medium bowl until evenly coated. Fold all but 1/2 cup blueberries into batter. Spread evenly into the prepared pan. Top with the remaining 1/2 cup blueberries. Sprinkle cane juice on top of the blueberries.

Bake in the preheated oven until cake is browned on top and a toothpick inserted into the center comes out clean, 70 to 75 minutes.

Let cake cool in the pan for 15 minutes, then unmold (remove the outer ring) and transfer to a wire rack to cool completely.