Make the cake: Arrange a rack in the middle of the oven and heat to 350°F. Coat 2 (8-inch) round cake pans with butter, then line the bottom of each with a parchment paper round; set aside.
Place the flour, almond meal, baking powder, and salt in a medium bowl and whisk to combine; set aside.
Place the marzipan and sugar in a food processor fitted with the blade attachment and pulse until it is the texture of coarse meal.
Transfer to the bowl of a stand mixer fitted with the beater attachment. (Alternatively, use an electric hand mixer and large bowl.) Add the butter and beat on medium speed until light and fluffy, 3 to 4 minutes.
Reduce the speed to low and add the eggs one at a time, waiting until each egg is incorporated before adding the next. Beat in the vanilla and almond extracts. Add the flour mixture and beat until just incorporated.
Remove the bowl from the mixer, add the sour cream and fold it in with a rubber spatula until just incorporated.
Divide the batter evenly between the cake pans. Bake until the top bounces back when you gently press it, or a toothpick comes out clean when inserted into the center of the cake, 35 to 40 minutes.
Place the pans on a wire rack and let sit until cool enough to handle, about 20 minutes. Run a thin knife around the edges of the cake to loosen, flip the cakes out, remove the parchment paper, and then place right-side up back on the rack to cool completely before filling and frosting. Meanwhile, make the marzipan cut-outs.
Make the marzipan cut-outs: Knead food coloring into the marzipan for each color you desire. Roll each piece of colored marzipan on a work surface dusted with powdered sugar until 1/8- to 1/16-inch thick. Cut into desired shapes with a knife or cookie cutters; set aside.
Make the buttercream: Place the butter in the bowl of a stand mixer fitted with the paddle attachment. (Alternatively, use an electric hand mixer.) Beat on medium speed until soft and smooth, 2 to 3 minutes.
Stop the mixer. Sift in the powdered sugar and beat on low speed until combined. Increase the speed to medium and beat until light, fluffy, and smooth, 1 to 2 minutes. Beat in the almond extract and salt.
Assemble and decorate the cake: If the cakes are not level, use a serrated knife to trim the tops.
Place 1 of the cakes on a cake or serving plate. Frost the top of the cake with 1/2 cup of the buttercream. Top with the second cake. Frost the top and sides of the cake with more buttercream to completely cover. Refrigerate for 10 minutes. Decorate with the marzipan cut-outs.
Make ahead: The cake layers can be baked ahead. Do not level the cakes. Wrap each one tightly in plastic wrap and store at room temperature for 1 day, or in the freezer for up to 1 week. Defrost before using.
Storage: The assembled cake can be covered in plastic wrap and stored in the refrigerator for up to 5 days.
Credits: Emily Petrick is a West Coast-based baker and food stylist. She is a Cordon Bleu graduate and worked at several prestigious Los Angeles bakeries before starting her own business. She is happiest when she is experimenting and making a mess in her kitchen. You can see more of her work on her website.