A normal Cake is made with eggs, flour, milk, sugar, butter and vanilla. This cake can be consumed by everyone. But people with the Celiac Disease cannot eat this cake, because this cake contain an ingredient which trigger the disease. So if you want to bake a cake for your friend who has this disease, you need to substitute Flour with gluten free flour. Gluten flour is the ingredient that triggers this disease. We can have other options or substitutes for flour as well that don't have gluten in it, like using oatmeal or oats instead of flour within the recipe.