Traditional panettone is made using 100% butter
Proper panettone is beautifully soft, flavourful and always made from butter. Cheap, imported panettone is made using margarine. In Italy, they take the butter thing so seriously it is actually illegal to sell panettone made with margarine, so it is exported. Always check the ingredients when picking a panettone and if you are still not sure...the good old taste test should settle it.