Preheat oven to 350° F. Grease two 6-inch cake pans and line the bottoms with parchment.
Mix together the sour cream and baking soda and set it aside.
In the bowl of an electric mixer fitted with a paddle attachment, cream together the butter and sugar until fluffy. Add the almond paste and beat at medium speed for 5 minutes. Add the egg yolks one at a time and mix until incorporated. Blend in the almond extract, the sour cream mixture, and the salt. Reduce mixer to low and gradually add the flour until just combined.
Divide the batter between the pans and spread it evenly. Bake for about 30 minutes, until the tops are browned and the edges shrink from the sides of the pan. The centers of the cakes will likely cave in a bit once they come out of the oven but that's okay. Let the cakes cool for a few minutes in their pans and then turn onto a wire rack to cool fully. You can wrap these in plastic wrap and keep them at room temperature for about a week or so.
Level the tops of the cakes, if needed. Spread a thick layer of jam on one layer and then place the other layer on top. Spread a thin layer of jam all over the entire cake.
Roll your marzipan out on a piece of parchment paper into a large circle, about 1/4-inch thick. Use the parchment to help get the marzipan sheet over the cake. Smooth the marzipan down over the cake and trim the edges. Knead food coloring into any excess marzipan and use it for decorations. Stick on your decorations, and complete the look with sprinkles!