Cakes, cupcakes, pancakes, banana breads, or desert bread, and muffins are very similar animals. They all rely on a basic ratio of ingredients to make them work. Here is the basic ratio that I use. I then modify accordingly to make the end product I want.
1 cup flour
1 large egg
3 tbs. double-acting baking powder
1/2 tsp. salt
3 tbs. cooking oil
3/4 cup of liquid
Cakes and cupcake crumb is finer than is the crumb of a quickbread or muffin. This is achieved by using a flour with more starch and less protien - cake flour. Sweetness is obtained by adding sugar, brown sugar, Sucralose, Stevia, or a sweet syrup. If using a syrup, you have to adjust the amount of water added to account for the water in the syrup. If adding chocolate flavor, use a dutched chocolate. The dutching process removes acid from the cocoa, giving it a neutral PH. If your chocolate isn't dutched, then you have to add baking soda to counteract the acidity of the cocoa. Acidic fruits are the same.
The egg adds body, and along with the starch and water, glues the crumb together. Too much protien can make the end product rubbery. Think of angel food cake, or sponge cakes. They are more elastic because they have a lot of eggs in the recipe. Salt ballances out the sweetness, and awakens the taste buds to the more complex flavors in the cake. The oil, not the water, is what gives the cake its moist feel in the mouth. You can substitute fruit and fiber for the oil, but too much of either will make the cake gummy instead of moist. Oil content is easier to control.
Fro a standard batch of cupcakes, or a typical nine inch cake, you will need three cups of flour. And by the basic recipe, this means you will need three large eggs, 3/8 cup of oil, 1 1/2 tsp. salt, and 3 tbs. baking powder. Typically, you would add 1 1/2 to 1 3/4 cups of sugar or equivalent sweetener and either 2 1/4 cups of milk or water. You can also substitute butter for oil. And most cakes, no matter what flavor, have a tsp of vanilla extract in them.
If you use all purpose flour instead of cake flour, it will still come out just fine, but not quite as delicate in crumb. The basic recipe is also great for making pancakes, with the addition of 2 tbs. sugar and 3/4 cup of milk.
Good luck to you. Try these tips and you are well on your way to making a host of cakes, cupcakes, quickbreads, pancakes, and other such great foods.
Seeeeeeeya; Goodweed of the North