Delicious recipe. I made the following changes: I used whole wheat flour (instead of white) and brown sugar instead of white as well as as raw sugar on the topping. I didn't have quite enough sour cream, so I added plain yogurt and I included a combination of blueberries, blackberries, strawberries and peaches. Yummy and not too naughty! Caveats: I sprayed the muffin tins, but they stuck to the bottom anyway. Not sure what is the norm for muffins, but in the future, I would either grease more or grease and flour the tins first. Also, I would add cinnamon to the recipe (instead of just being part of the topping and more lemon peel!

Nice flavor, nice texture, BUT needs at least another 1/4 cup of sugar or more. Not very sweet.