I find that no matter what the recipe, anytime I bake gluten-free, the cupcakes shrink. When I take them out of the oven, they are lovely, domed, very nice, then as they cool down, they shrink into little cakelets!
They shrink away from the edges of the pan by almost a quarter inch all around. THey are still soft and moist, just smaller and puny looking.
Any suggestions, or is this just what gluten free does? I use a gluten free baking mix and a touch of xantham gum.
I bake exclusively gluten free, and you cannot tell my baked goods from the gluten ones. I don't use commercial mixes as they don't produce the taste I want. But, suggestions: If your mix has xantham gum already in it, don't add any more. Even a little bit too much or too little can ruin your cake. GF cake mixes turn out better than general purpose flour mixes. Try lowering your oven temperature by 25 degrees and bake a little longer. That usually stops the shrinking.
I also exclusively bake Gluten-Free and haven't had that happen. But If you have even a bit too much moister in the cakes they will shrink as they cool. I've seen this happen to others. While they are warm or in the oven they remain up high and during cooling they shrink.
I don't recommend using boxed mixes, they aren't good. And you will have this issue more with boxed mixes then a good scratch recipe.
Like Carrie said the xanthan can also be an issue, too much, too little.
When using boxed mixes if it calls for certain extra added ingredients, eggs, water, milk, oil etc... If you substitute different ingredients, like juice or pudding mix you will run into problems. Gluten-Free isn't as forgiving as regular baking with added or replaced ingredients.
It will require some trial and error to perfect. It isn't as simple as people think.