Step 1: Preheat your oven to 350°F (175°C). Grease and flour your 9-inch round cake pan, ensuring the cake will slide out easily once baked.
Step 2: In a large mixing bowl, whisk together the 3 eggs and 1 cup sugar until the mixture is light and fluffy. Gradually add in the 1 cup 2% milk, 1 cup extra virgin olive oil, and 1 tsp lemon extract. Mix until well combined.
Step 3: In another bowl, whisk together the 1 cup flour, 1 cup cornmeal, 1 tsp baking soda, 1 tsp baking powder, and 1/2 tsp kosher salt.
Step 4: Slowly add the dry mixture to the wet ingredients, stirring gently until just combined. Be careful not to overmix, as this can lead to a dense cake.
Step 5: Gently fold in the 1 cup blackberries with a rubber spatula, taking care not to break them up too much.
Step 6: Pour the batter into your prepared cake pan. Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean.
Step 7: Allow the cake to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely. Serve it as is, or dust with powdered sugar for an elegant touch.