Using your cake leveler, remove the tops from each cake for a smooth, flat building surface. Save these cake scraps for snacking, or creating cake balls!
Brush the maple simple syrup generously onto each layer of cake with the silicone pastry brush.
Cut a wide opening in a piping bag (you don't need a tip for this) and create a ring of buttercream around the top edge of your bottom cake layer. This will create a dam, into which you will spoon out and smooth about half of the apple pie filling. (If you are using six cake layers instead of three, read the next step/note below, before moving on with this step.) Gently place your second layer of cake onto the bottom layer, and repeat the process again, piping a ring of buttercream and filling it with apple pie filling. To top your cake, invert the final layer so the bottom is facing upwards. This creates a smoother top for frosting and decorating.
NOTE: If you are using six layers of cake instead of three, stack the layers into three sets of two cakes each, with a thin layer of buttercream spread in the middle of each one. Then, use these stacks of two as "one" layer for building with the apple pie filling in the step above. This way, your cake remains balanced with the fillings and stays structurally sound as well.
Apply some white frosting to the top of the cake, using your offset spatula to smooth it out and begin to push it over the edges. Apply more buttercream to the sides, as needed. Then, with your bench scraper at a tight, close angle to the side of your cake, begin to smooth the sides of the cake. This first coat doesn't have to be perfect, and cake is likely to show through - that's fine. This "crumb coat" locks in the cake crumbs and provides a smooth canvas for your final coat. Place the cake in the refrigerator for 20-30 minutes to let the crumb coat harden to touch.
Meanwhile, tint buttercream with your food coloring gel and mix to your liking for your final coat. Once the cake is chilled, repeat the process again, in a similar manner as the crumb coat, but this time, with your final buttercream color. Smooth the top and edges out, and use your offset spatula to add frosting to any holes or dents. Keep scraping around until you are happy with this top coat.
To smooth the corner edges of the cake, hold your offset spatula parallel to the top of the cake, and gently but decisively push the buttercream off of the edge and in towards the center. Wipe your spatula on a towel and repeat. Chill the cake while you prepare your buttercream flowers.
To create beautiful buttercream flowers, fill piping bags (fitted with couplers) with colored, stiff buttercream. Use a small bit of frosting to attach a parchment paper square to the flower nail. Moving in short strokes, pipe the flower pattern according to my video, depending upon the flower you wish to create. See my diagram below for the piping tips you'll use. Gently slide the parchment paper off of the nail, onto a flat surface like a baking sheet. Once the baking sheet is full, place it in the freezer until they're hardened. Once the flowers are solid, you can use a bit of buttercream as glue to attach them to the cake. Simply peel off the parchment paper and adhere it like a sticker!
Print out or draw a sketch of a monarch butterfly. Lay a piece of parchment paper over it. Then, roll out and color some black fondant. Make thin long tubes, and lay it over the parchment paper to outline the monarch. Then, add the smaller black lines by creating thinner, shorter tubes of thin fondant. Next, slide out the drawing of the monarch, and place it over a piece of thin, orange fondant. Cut out the body shape of the monarch, and place it over the black lines. Use a rolling pin to flatten the fondant slightly, adhering the orange to the black, combing it into one piece. Using some smaller white pieces, and more black if necessary, add more details, pressing them in with your finger or a food-grade paintbrush. Roll a larger piece of black fondant into an oblong shape to create the butterfly body. Insert your wire into the body, then attach it to the wings. Place the butterfly in between two angled drying racks, forks, or the edges of a small plate to shape it as if it were flying. Let dry for at least 24 hours, more if your pieces are thick. Once completey dried, you can go back and add smaller details with a food-grade paintbrush and food coloring gels as the "paint." Gently press down into the cake to place.
Store the cake covered at room temperature for up to 4 days. However, remove the butterflies and store them uncovered at room temperature, otherwise, the moisture from the cake may cause them to become gummy and gooey. You can also freeze the cake or individual slices for up to 2 months. In frozen, thaw in the refrigerator for 12-24 hours (depending upon the size) before serving.