Preheat the oven to 350F and spray a 9"x5" loaf pan with nonstick spray. In a large bowl, stir together the dry ingredients. Cut in the butter until the mixture is evenly crumbly. (Idea: you could do this in the food processor, and make dry mixes in advance to keep in the freezer; add the egg, juice and berries when you want to bake it!)
Add the egg, zest and juice and stir until almost combined; add the cranberries and raisins and stir just until the batter comes together.
Spread into the pan and bake for about an hour, until the top is springy to the touch.