Preheat Oven and Prepare Pans - Preheat oven to 350 degrees Fahrenheit and grease pans.
Sift Dry Ingredients - Sift the flour, baking soda, and salt.
Cream Butter and Sugar - With an electric mixer, beat the butter until smooth and add the sugar, mixing for 3-4 minutes. Add the vanilla, eggs, and also egg yolk, mixing until combined.
Add the Flour Mixture and Divide - Add half of the flour mixture and slowly pour in the milk. Then, add the rest of the flour mixture and mix until combined. Separate the batter into two bowls.
In one of the bowls, mix together the lemon zest, lemon juice, and yellow food coloring. In the other bowl, fold in the strawberry preserves and pink food coloring. Then, pour the two colors into two cake pans each.
Bake and Assemble - Bake the cakes for 22-25 minutes and allow them to cool for 15 minutes. Using a serrated knife, carefully trim the tops of the cakes to make them level.
Use the 4-inch cookie cutter to cut out the centers of the cake. Then, use the 2-inch cutter to cut the centers of the 4-inch cakes. For the first and third layer, start with strawberry, then lemon, and then strawberry, alternating for the second and fourth layer.
Place the cakes on top of each other with a layer of buttercream in between each. Decorate the rest of the cake with buttercream.