4.

To Make the Cake: In the bowl of a stand mixer fitted with a coated paddle attachment (raw-aluminum attachments may discolor the batter, particularly if the attachment has ever gone through a dishwasher, in which case it may also impart an unwanted flavor), combine butter, sugar, baking powder, baking soda, salt, and cinnamon. Please note, the mixing times and temperatures suggested for this recipe are based on the use of a stand mixer; for hand-mixing, substantially warmer temperatures may be required, and mixing times will vary by as much as 200% or more depending on the horsepower of the machine in question, as well as its beater design and RPMs. Mix on low speed to roughly incorporate, then increase to medium and beat until fluffy and light, about 5 minutes. Be aware that this is not a process that can be judged by time alone. Times are listed only as an approximation, based on the listed ingredients, ingredient temperatures, and equipment, and on an average room temperature of 70°F (21°C). However, the author does not mean to suggest that bakers maintain a 70°F (21°C) environment in the kitchen at all times; only that substantially different ambient conditions will affect the results of this or any other recipe, as batter temperature is largely determined by ingredient temperature, as well as the temperature of the equipment that comes into contact with said ingredients. For example, in a kitchen with sustained temperatures in the mid-80s, the mixing bowl and sugar will both reach a temperature of 80°F (27°C), which is warm enough to initiate melt in butter. Please note that the reverse is just as true, and equally problematic. This is not a special consideration for this recipe, but rather a universal truth for any recipe based on an ingredient that can exhibit a wide variety of textural changes based on the variety of temperatures commonly seen in human habitation.