This Neapolitan cake is made with strawberry, vanilla and chocolate cake layers that’s filled with Swiss Meringue Buttercream
Preheat the oven to 350 °F. Spray three 6-inch round cake pans with non-stick spray, line the bottom of each pan with parchment paper and spray again. Set aside.
In a medium-size bowl, whisk and stir together the flour, baking powder, and salt. Set aside.
In the stand mixer bowl fitted with a paddle attachment, beat the butter, oil, and sugar on medium-high for 5 minutes.
Add the eggs, one at a time to the stand mixer bowl and beat on medium until well incorporated.
Turn the mixer on low and add the flour mixture to the butter mixture until fully incorporated.
Pour in the buttermilk and vanilla extract. Mix on medium for another 30 seconds and scrape down the sides of the bowl.
Evenly distribute the cake batter into three mixing bowls. In one bowl, add ⅓ cup sifted cocoa powder and mix until combined. In another bowl, add ½ cup strawberry preserves and 1-2 drops of super red gel food coloring and mix until combined.
Add the cake batter into three cake pans, one flavor per pan. Bake for about 35-40 minutes or until a toothpick inserted into the center of each cake comes out clean or with just a few moist crumbs.
Remove cakes from the oven and let cool in pans for 10 minutes before inverting onto cooling racks to cool completely. Wrap cakes in plastic wrap and place them into the freezer to chill for 30 minutes to 1 hour.
On the stovetop, place a medium saucepot filled ⅓ of the way with water over medium heat, bring to a simmer to use as a double boiler.
In a stand mixer bowl (or large glass or metal mixing bowl), add egg whites and sugar mix with a whisk to combine.
Lower the heat on the stove to low, then place the mixer bowl over simmering water. Whisk constantly to prevent eggs from overcooking, continue for 3-5 minutes.
Continue to whisk until the mixture has reached 160 °F on your candy thermometer. Or until the sugar has dissolved between your fingertips.
Immediately remove from the heat and transfer to the stand mixer with the whisk attachment and add the salt. Begin to mix on medium-high speed to create a light meringue for 10 minutes.
Mix until the meringue is room temperature and has a stiff peak.
Next, lower the mixer speed to low and add the butter a few cubes at a time until all the butter is incorporated into the meringue.
Then whisk on medium speed until the mixture is thick and creamy. It'll look like freshly whipped butter.
With a rubber spatula, add vanilla extract and mix by hand until incorporated.
Divide the buttercream into three mixing bowls (1 ½ cups per bowl). In one bowl, add melted chocolate that has cooled slighted and mix until well incorporated.
In another mixing bowl, combine strawberry preserves and 1-2 drops of super red gel food coloring, mix until well incorporated. Leave the last bowl white for vanilla buttercream. Now you should have chocolate, strawberry and vanilla buttercream.
Finally, place the buttercreams into the refrigerator for 10-15 minutes to set the buttercream before using it.
Remove the cake layers from the freezer and unwrap the cake layers. Next, use a serrated knife to cut off the dome of the cakes to make the layers flat and even.
Add a small amount of vanilla buttercream onto the center of the cake board. Layer one cake layer, cut side up onto the cake board.
Pipe a ring of chocolate buttercream in the center of the cake. Followed by rings of vanilla and strawberry buttercream on the outside. Use an offset spatula to smooth the buttercream layer.
Place another cake layer cut side down over the top. Repeat the process for another layer — Crumb coat with white buttercream and freeze for 30 minutes.
On the frozen cake, start from the bottom and pipe several rows of chocolate buttercream then add a few rows of vanilla buttercream in the middle of the cake.
Repeat by adding strawberry buttercream on the top part of the cake. Use an offset spatula and cake scraper to make the sides and the top as smooth as possible. Fill in any air bubbles with the coordinating buttercream flavor.
Continue to use the offset spatula and cake scraper to smooth the sides and top of the cake. Place the cake into the refrigerator to set the buttercream for 15 minutes.
Serve at room temperature and enjoy!