2. If the cake is a single layer, set the cake flat side up on a cardboard round (if you have one) or flat serving plate. If it is two or three layers, set the first layer flat side down. (If your cake layers have excessively high domes, you should slice the dome off with a serrated knife so the cake will sit evenly.) Lightly brush off all crumbs with a soft pastry brush.
3. Tear small strips of wax paper and tuck them under the bottom layer, leaving about an inch of paper exposed around the cake. This is to keep the frosting off the serving piece.
4. If you are frosting a two-layer cake, spread about 1/2-inch of frosting over the bottom layer with an offset spatula held at a slight angle. Place the second layer over the frosting, flat side up. For either one- or two-layer cakes, frost the top, then the sides, using the spatula to draw and smooth the frosting over the surface of the cake, holding back about 1/4 of the frosting.
5. Put the cake in the fridge for about 10 minutes to set the frosting and prevent crumbs from getting mixed in.
6. Place spoonfuls of the remaining frosting on the top of the cake. Add frosting to the sides, if needed, and smooth with the spatula held at a 90 degree angle. Spread the frosting on the top, using the back of a spoon or offset spatula to create peaks and valleys, if desired, aiming for a beautiful and even finish.
7. Remove the wax paper before serving.