1. Each cake layer needs a sturdy base. Trace cake pans onto a piece of foam board three-sixteenths of an inch thick. Cut out the rounds (available at art-supply stores). Bake cakes in parchment-lined cake pans, and let them cool slightly. Remove from pans. Do not peel off parchment. Once completely cool, place each cake right side up on a foam-board round, wrap in plastic, and refrigerate for at least 6 hours; this makes the layers firm and easy to handle. They can also be frozen at this point.

2. If a cake doesn't bake level -- they often don't -- even it out with a serrated knife. Use a turntable to make it even all around.

3. Place a small dollop of the buttercream in the center of the cake. Put another foam-board round on top of the tier; invert the cake onto the foam board. Remove the original foam-board base and parchment. The bottom of the cake is now the top; the cake will remain on this foam-board round from now on.

4. Split the cake. Hold a serrated knife against the edge of the cake; rotate the turntable, working the knife through the cake.

5. Brush the cut surface of the bottom half of the cake with a sugar syrup, flavored with liqueur or orange zest if desired. This syrup will moisten the cake and add a subtle flavor.

6. Pipe the buttercream around the perimeter of the bottom half of the cake. Use a pastry bag fitted with a standard-size coupler. This "dam" will keep the jam filling in place.

7. Fill the bottom layer with jam filling one-eighth of an inch thick; don't use so much that the top layer slips and slides.

8. Carefully replace the top layer, cut side down, and brush with sugar syrup. Then let set for 2 to 3 minutes.

9. Ice the top with buttercream using an offset spatula to give the tier a "crumb coat." This thin layer of icing will seal the cake. Start from the center and work out, making sure to push the buttercream over the sides of the tier.