Many cake recipes call for greasing and flouring the pan before adding the batter. This step helps to keep the cake from sticking to the pan after it bakes, and often gives the batter something to "cling to" as it rises in the oven to give the cake better volume.
It's simple: Rub the inside of the pan with butter (there should be enough left on the wrapper; you only need a thin coat). Spoon in a tablespoon or so of flour and, working over the sink to catch any spillage, tap the pan to distribute the flour first across the bottom and then, tilting it, along the sides. Discard any that's left over. You should see a very light film of flour clinging to the interior of the pan.
If you're making a chocolate cake, consider replacing the flour with cocoa powder. Not only will the cocoa powder keep you from having to worry about the white film left by flour on a finished cake, it'll also give you a little extra depth of flavor.
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