• Preheat the oven to 180°C/350°F.Place a rack in the center of the oven.
• Grease a round 27 cm/10.5 inchesspringform pan with a piece of butter and line the bottom and edges with a piece of parchment paper.
• For the filling, combine the blueberries, sugar and cinnamon powder. Set aside.

For the cake batter:

• Combine the flour, baking powder and salt. Set aside.
• Cream the butter and sugar in an electric mixer for 2 minutes.
• Add the egg, egg white and vanilla extract and continue beating on high speed for 2 minutes.
• Reduce the speed to very low and slowly add the milk and flour and mix just to integrate the batter.
• With a rubber spatula, scrape down the sides of the bowl and mix slowly one more time.
• Spread half of the batter onto the greased lined springform pan. Sprinkle the blueberry filling, fully covering the batter.
• Spread the remaining batter on top, fully covering the blueberries.
• Bake in the oven about 45-50 minutes, or until you insert a toothpick in the center of the cake and it comes out clean. Enjoy it!