Apple Butter Cake with Rye and Farro Flour

This cake began as the Muscovado Sugar Cake from Kim Boyce’s fantastic baking book Good to the Grain. Published in 2010, the book features recipes for pastries, cakes, and cookies made with whole grains. I’ve made a couple of tweaks along the way but have stayed true to Kim’s original recipe. Muscovado sugar is a less-processed version of brown sugar. I…