Fill your cupcake liners about 2/3 to 3/4 full with batter. Overfilling the liners can cause the batter to spill over the edges and create a domed top. Tap the pan gently on the counter a few times to settle the batter after the cups are filled. If your cupcakes always seem to come out with a dome, try lowering the oven temperature by 25 degrees.