01 - Preheat oven to 350°F. Grease and flour a 9-inch round cake pan or line with parchment paper.
02 - In a medium bowl, whisk together all-purpose flour, baking powder, baking soda, and salt. Set aside.
03 - In a large mixing bowl, beat unsalted butter and granulated sugar together until light and fluffy.
04 - Add ricotta cheese to the creamed mixture and beat until smooth.
05 - Mix in eggs one at a time, beating well after each addition. Stir in vanilla extract and lemon zest if using.
06 - Add half of the dry ingredients to the ricotta mixture and mix gently. Pour in the whole milk, mixing until just combined. Add remaining dry ingredients and mix until smooth without overmixing.
07 - Gently fold fresh or frozen blueberries into the batter using a spatula.
08 - Transfer batter to the prepared cake pan and smooth the top. Bake for 40 to 45 minutes, until a toothpick inserted in the center comes out clean and the top turns golden brown.
09 - Allow cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.