Heat the oven to 335 degrees F and line the bottom of a 9 inch springform pan with parchment paper. Spray the pan with spray oil.

Toss the blueberries with the cornstarch in a bowl and set aside.

In the bowl of a stand mixer, cream the butter, sugar, vanilla, and lemon zest with the paddle attachment until fluffy and light. Scrape down the sides of the bowl.

Add the eggs, one at a time, and mix each one in thoroughly.

Add the ricotta and mix until the batter is thoroughly mixed.

In another bowl, whisk together the flour, almond flour, baking powder, and salt. Using a strainer, sift the dry ingredients into the butter/sugar/egg mixture and then fold with a rubber spatula until combined.

Fold in 2 ½ cups of the blueberries and spread the batter in the pan. Top with the remaining blueberries.

Bake the cake for 80 to 90 minutes, until a toothpick comes out clean. My baking time was 80 minutes.

Cool the cake on a wire rack until it is just slightly warm. Dust with the powdered sugar before serving.