Here are my tweaks:
I used Namaste gluten-free baking flour, doubled the butter to 1 cup, did not use the streusel, and baked for 20 minutes at 350F.
The recipe above is in a little book that Micaela made for me with a few of her favorite recipes. All the ones I have tried are delectable. She took an old spiral-bound Campbell's Soup promotional cookbook and added some new pages in the front. They are all handwritten, and thus easily smeared, but next time I will cover the page with plastic wrap before I start.