When beating butter and sugar your butter should be soft but still have a little give to it when squeezed. Butter and sugar are beaten together to introduce lots of air and this is critical to achieving a light and airy cake. After about 1-2 minutes of beating on a medium-high setting, your butter and sugar mixture will become pale yellow in colour and light and soft in texture, if you are using a stand mixer, you will start to notice it sticking to the sides of the bowl, this is the point at which you can stop beating. Add too much air and the texture of your baked cake will suffer.