Preheat the oven to 350°F (175°C). Prepare a 9×13-inch rectangular cake pan by spritzing it with vegetable oil and lining with a parchment paper rectangle cut to size, and then spritzing again with oil.

In a large bowl, whisk the soy milk, sour cream, aquafaba, and vanilla extract together until combined and frothy.

In the bowl of a stand mixer, mix together the cake flour, sugar, baking powder, baking soda, and salt until combined.

With the mixer on low speed, add the butter, 1-inch pieces at a time. The mixture should clump up.

Pour in half of the whipped milk mixture, mixing for about 15 seconds. Then pour in the remaining milk mixture and mix until a smooth batter forms.

Pour the batter into the prepared cake pan and bake for 30 to 34 minutes, until lightly browned and a toothpick comes out with moist crumbs.

Let the cake cool completely in its pan on a wire rack.

In a small saucepan, combine the soy milk, sugar, vanilla extract, and salt for the vanilla milk soak, stirring until the sugar has dissolved. Let cool completely.

Trim off any dome from the cake. Brush the vanilla milk soak all over the cake.

Apply a thin layer of jam on the entire cake. Spread a layer of vanilla Swiss meringue buttercream on top.

Dot the cake with fresh raspberries.

Divide the remaining buttercream between four bowls and tint each with gel colors. Pipe an assortment of different-sized drop stars and rosettes all over the cake.

Chill the cake for 30 minutes before slicing.