• Start by preheating your oven to 325°F (163°C). Prepare three 8-inch cake pans by greasing them thoroughly, dusting with flour, and lining the bottom with parchment or wax paper for easy release.
• In a medium bowl, combine the flour, baking powder, baking soda, and salt. Whisk these ingredients together for about 30 seconds to ensure everything is evenly distributed. Set this dry mixture aside for later use.
• Next, grab another bowl for the wet ingredients. Pour in the buttermilk, vegetable oil, lemon zest, and lemon extract. Give it a good stir and set it aside.
• In the bowl of your stand mixer, beat the butter and softened cream cheese on medium speed until it’s smooth and creamy. Gradually add the sugar while continuing to mix for 2-3 minutes.
• Begin adding the eggs, one at a time, allowing each to fully incorporate before adding the next. Mix until the yolks are no longer visible.
• Reduce the mixer speed to low. Alternately add the dry ingredients and the buttermilk mixture, starting and ending with the dry ingredients. Be sure to scrape the sides of the bowl as needed. Mix just until everything is combined, being careful not to overmix.

Prepare the Raspberry Swirl

• Scoop out 1 cup of the cake batter into a separate small bowl. Stir in the raspberry jam along with the raspberry extract or Jell-o powder, if you're using it. If desired, add a little red or pink food coloring to enhance the swirl.

Fill the Cake Pans

• You’ll have about 6 cups of plain batter and a little more than 1 cup of raspberry batter. Divide approximately 1 heaping cup of the plain batter into each of the prepared pans. Then, spoon some of the raspberry batter over the plain batter, distributing it evenly across the pans.
• Add the remaining plain batter to the pans, followed by any leftover raspberry batter. Use a knife to swirl the batters together, creating a marbled effect. Tap the pans lightly on the counter to settle the batter.
• Bake for 28-30 minutes, or until a toothpick inserted in the center of each cake comes out clean or with a few moist crumbs attached. Allow the cakes to cool in the pans on a wire rack for 5-10 minutes before turning them out to cool completely.

Sweetened Whipped Cream Filling

• Before you start, place your mixing bowl and whisk attachment in the freezer for about 10 minutes to chill them. Once ready, pour the heavy cream, confectioners sugar, and vanilla into the chilled bowl. Begin beating on low speed, gradually increasing to medium-high. As the cream thickens, soft peaks will form, which should take about 1½ minutes. Keep a close eye on it to avoid overbeating.

Cream Cheese Frosting

• In your mixer bowl, beat the butter slices on low to medium speed until they’re soft and smooth. Add the cream cheese, a few pieces at a time, and continue beating until fully incorporated.
• Add the lemon extract, followed by the confectioners sugar, a little at a time. Beat on low speed until combined, then increase the speed slightly and continue mixing until the frosting is fluffy. For best results, use this frosting while it’s still slightly chilled.

Assemble the Cake

• Place the first layer of cake on your serving plate or stand. Pipe a border of cream cheese frosting around the outer edge of the cake. Inside this border, spread a thin layer of raspberry jam, followed by a layer of whipped cream filling.
• Repeat the process with the second cake layer. After placing the third layer on top, fill in any gaps between the layers with frosting. Apply a thin crumb coat of frosting to the entire cake, then chill it in the freezer for 10-15 minutes (or refrigerate for longer).
• Once chilled, apply the final layer of frosting, smoothing it with an offset spatula. If desired, use the spatula to create a textured finish. Garnish the top with fresh raspberries for an extra touch of elegance.