Prepare the Cake Pans: Preheat the oven to 350°F (177°C). Line two 8-inch cake pans with parchment paper, leaving the sides ungreased.
Mix the Wet Ingredients: In a large mixing bowl, combine the canola oil, whole milk, eggs, sugar, and vanilla extract. Beat with a hand mixer, stand mixer, or whisk on high speed for 2 to 3 minutes, until the eggs are thoroughly beaten and the mixture is well combined. Combine the Dry Ingredients: In a separate bowl, combine the all-purpose flour, baking soda, baking powder, and salt. Sift the dry mixture into the wet ingredients.
Finish the Cake Batter: Mix the batter on medium speed for about 1 minute, stopping as soon as the flour is incorporated. Avoid mixing beyond this point.
Add Lemon Zest: Zest 2 to 3 lemons and add the zest to the prepared cake batter.
Coat the Raspberries: Place the raspberries in a small bowl and toss them gently with the cornstarch until the berries are evenly coated.
Fold in the Raspberries: Using a spatula, gently fold the cornstarch-coated raspberries and lemon zest into the cake batter, taking care not to crush the berries unnecessarily.
Bake the Cake Layers: Divide the batter evenly between the two prepared cake pans. Bake at 350°F (177°C) for 32 to 35 minutes, or until a toothpick inserted into the center comes out clean.
Cool the Cake: Let the baked layers cool in their pans for about 20 minutes. Transfer them to a wire rack and allow them to cool completely before assembling the cake.
Prepare the Lemon Juice: While the cake is baking, freshly squeeze the lemons for the curd. Double-strain the juice for the smoothest texture, then set it aside.
Whisk the Curd Base: In a medium stainless-steel saucepan, combine the eggs, egg yolks, and granulated sugar. Whisk vigorously for 3 to 4 minutes, until the mixture becomes thick and pale and falls from the whisk in ribbons. Add the Lemon Juice: Pour the strained lemon juice into the egg mixture and whisk until evenly combined.
Cook the Lemon Curd: Place the saucepan over medium-low heat. Stir constantly along the bottom of the pan and cook for 4 to 5 minutes, until the curd thickens and begins to bubble lightly.
Finish the Curd: Remove the saucepan from the heat immediately. Add the unsalted butter and vanilla extract, then whisk until the butter has completely melted and the curd is smooth.
Cool the Lemon Curd: Transfer the curd to a glass bowl or glass jar. Cover the surface with plastic wrap to prevent a film from forming. Let it cool slightly, then refrigerate until completely chilled. Store-bought prepared lemon curd can be used instead if needed. Soften the Frosting Ingredients: Once the cake layers are cooled, make the frosting. Bring the butter and cream cheese to room temperature until they are slightly soft to the touch, but not melted or overly soft. If preparing the frosting in advance, keep it refrigerated until ready to use. Whip the Butter: Place the softened butter in the bowl of a stand mixer fitted with a whisk attachment. Whisk on high speed for about 5 minutes, frequently scraping down the sides of the bowl, until the butter is thoroughly creamed. Blend in the Cream Cheese: Add the softened cream cheese and whisk for another 2 to 3 minutes, scraping the bowl as needed, until the mixture is smooth and uniform.
Sweeten the Frosting: Add the vanilla extract, salt, and confectioners' sugar. Begin whisking on low speed until the sugar is incorporated, then increase to high speed and whisk for 2 to 3 minutes, until the frosting is light and fluffy. Add Lemon Zest: Add the lemon zest and whisk for another 30 seconds. For a stronger lemon flavor, the source also notes that 1 teaspoon lemon oil, 1 tablespoon lemon juice, or 1 teaspoon citric acid may be added.
Level the Cake Layers: Once the cake layers are completely cool, use a long serrated knife to level them if necessary.
Fill the First Layer: Place the first cake layer on your work surface or serving base. Spread a generous layer of lemon frosting evenly over the top. Add a few tablespoons of lemon curd to the center, spreading it outward while keeping the curd within 1/2 inch of the cake's edge. Stack the Cake: Place the second cake layer on top of the filling. Frost the top and sides of the assembled cake, smoothing the frosting with cake spatulas.
Apply the Crumb Coat: Cover the cake with a thin crumb coat of frosting, then refrigerate it for 15 to 20 minutes before applying the final layer of frosting.
Finish the Cake: Apply the final coat of frosting to the chilled cake and smooth the top and sides with cake spatulas.
Garnish the Cake: Decorate the top with additional lemon curd and 1 cup of fresh raspberries.
Store Before Serving: If the cake will not be served within a few hours, keep it refrigerated. When ready to serve, remove it from the refrigerator and let it stand at room temperature for about 1 hour to soften. The well-covered cake can be stored in the refrigerator for up to 4 to 5 days.
