You may notice that this recipe uses a lot of fat in the forms of butter, oil, or buttermilk; this is what keeps a gluten-free cake moist. In fact, there's very little difference between this cake and a regular Texas sheet cake made with gluten flour. However, due to the fact that most gluten-free products have a naturally shorter shelf life, proper storage in an airtight container, as I will talk about below, is essential for maintaining that moisture content.