If you made the cakes the night before, take them out of the refrigerator and let them come to room temperature. Or wait until the cakes have cooled completely. Place one cake on a portable flat surface like a cardboard cake round, the bottom side of a plate, or anything else you have on hand. I used a round wooden surface.
Place that on top of a cake turntable or use your microwave plate and wheel to make a turntable (just take the wheel off, place it on the counter, and then put the microwave plate back on top of it). If you feel it’s necessary, you can even out your cakes before moving on.
Use a pastry brush to coat the top of the cake with the rosemary simple syrup.
Put some frosting in a pastry bag with a round tip (I used 2A). Pipe a protective border around the edge of the cake.
Spread the apricot compote onto the cake, making sure it doesn’t get higher than the frosting border you piped.
Place the second cake layer on top, lining it up carefully. Repeat steps 3-5 until you have all your layers done.
Place 1 cup of frosting on top of the cake and start spreading it out in a thin layer, using a pastry scraper and the turntable to spread the frosting around. It’s okay if crumbs get loose and it’s messy-it’s the crumb coat. You should be able to see the cake peeking through the frosting. Use more frosting if necessary.
Put the cake in the fridge for 30 minutes to allow the crumb coat to set.
Take the cake out again, place it on the turntable and add big dollops of frosting all around. Take a pastry scraper, hold it vertically and at a slight angle to the cake, and start turning the cake around. Keep going until excess frosting no longer coats the scraper and the cake is smooth.
Garnish with dehydrated lemon slices* and strands of rosemary.
Store the cake covered at room temperature or in the fridge for 3 to 5 days.