Prepare a 9×13 sheet pan with butter and parchment paper and set it aside.
Make the vanilla cake first.
Split the batter equally into two bowls.
Add 1 cup of strawberry preserves into one of the batter bowls.
Stir the preserves until it’s fully blended.
Set the vanilla and strawberry batters in the fridge.
Next, make the chocolate cake batter.
Once all three cake batters are made, pour a line of the vanilla batter in the prepared pan, then chocolate, then strawberry, and alternate until the pan are filled. You'll have extra chocolate cake batter that doesn't have to be used.
Bake in a preheated 350-degree oven for 30 minutes.
Don’t worry if the layers are not perfectly even, then will cook together still creating a Neapolitan look.