Preheat oven to 350 degrees Fahrenheit.
Spray each cake pan with nonstick cooking spray. Place a 9-inch parchment cake circle on the bottom of each pan, spray again, and flour, rotating the pans to coat evenly. Dump out the excess flour.
Each pan will need 2 concentric circles of foil, one from the 15 inch piece and one from the 21 inch piece.
Fold one of the 15-inch pieces of foil lengthwise in half. Fold again lengthwise in half, keeping edges straight. Fold one more time to make a strip approximately 1-inch high.
Using a round bowl approximately 3 inches in diameter, fold the strip around the bowl until the foil forms a three inch diameter circle. Secure the strip with a paperclip.
Repeat steps 3 and 4 two more times to make a total of three 3-inch diameter circles.
Fold one of the 21-inch pieces of foil lengthwise in half. Fold again lengthwise in half, keeping edges straight. Fold one more time to make a strip approximately 1-inch high.
Using a round bowl approximately 6 inches in diameter, fold the strip around the bowl until the foil forms a six inch diameter circle. Secure the strip with a paperclip.
Repeat steps 6 and 7 two more times to make a total of three 6-inch diameter circles.
Take 1 of each size foil circles and place them inside each other in the centers of each prepared pan, being careful to create approximately 1 inch of space between each and the edge of the cake pan.
Divide Chef Gail’s Yellow Cake between 2 bowls. Color each bowl of batter a different color using food coloring.
Place a large, plain pastry tip inside a large pastry bag and fill halfway with the first color batter. Pipe the batter into the outer circle of one pan, as well as the inner most circle, so that the middle space remains empty. Using a small offset spatula, gently spread the batter so it completely covers the bottom of each space. Do not remove the foil yet. Fill the middle space with the second color batter also placed into a pastry bag, and again smooth with a small offset spatula.
Repeat step 11 for one of the remaining two pans, refilling the pastry bags as necessary with their respective colored batters. This will create two identically colored pans of batter.
For the last pan, follow step 11 but alternate colors, so that this layer is in the opposite colors of the other two.
Gently lift the foil circles and dispose.
Bake cakes for 25-28 minutes, or until a sharp knife inserted into the center comes out clean.
Allow cakes to cool until barely warm, and remove from pans. Place cakes on cardboard cake circles.
The differently colored cake layer should be placed in the middle of the two identical ones when frosting. Decorate as desired.