‘all recipes’ has some great recipes and many of them are low-fat. Also in many cake/ muffin recipes you can replace most or all of the fat (marg or oil) with applesauce, measure for measure, and the taste & texture will be great. I usually recommend replacing half of the fat first (if it calls for marg, you can replace the other half with oil). If that works (which it usually does) then I’ll try a total replacement.
I do have a great banana oatmeal muffin recipe that I got from ‘all recipes’, and made some changes, if you’re interested I’ll post it after Shabbos.