1️⃣ Prepare Cake Pans and Preheat Oven:
Preheat your oven to 350°F (175°C). Grease and flour three 8-inch round cake pans and line the bottoms with parchment paper. Set aside.

2️⃣ Combine Dry Ingredients:
In a large bowl, whisk together the flour, sugar, cornstarch, baking powder, baking soda, and salt.

3️⃣ Add Butter:
Using an electric mixer on low speed, add the softened butter one piece at a time, allowing each piece to fully combine before adding the next. The mixture should resemble a sandy texture.

4️⃣ Add Oil:
While mixing on low speed, slowly drizzle in the oil, blending until just combined.

5️⃣ Mix Wet Ingredients Separately:
In a separate bowl or measuring cup, whisk together the buttermilk, lemon zest, lemon juice, eggs, and vanilla extract until smooth and well combined.

6️⃣ Combine Wet and Dry Mixtures:
With the mixer on low, gradually add the buttermilk mixture to the flour mixture. Continue mixing until the batter is smooth and fully combined.

7️⃣ Fold in Blueberries:
Use a spatula to gently fold the blueberries into the batter, distributing them evenly.

8️⃣ Divide and Bake:
Evenly divide the batter among the three prepared cake pans. Bake in the preheated oven for about 30 minutes, or until the top springs back when touched and a toothpick inserted in the center comes out mostly clean with a few moist crumbs.

9️⃣ Cool the Cakes:
Allow the cakes to cool in their pans for 10-15 minutes. Then, run a knife around the edges, invert the cakes onto a cooling rack, and let them cool completely.

🔟 Frost and Serve:
Once the cakes are completely cool, stack and frost them with lemon frosting or your preferred frosting. Serve immediately or store in an airtight container.