Serve this hearty bread with our White Bean and Roasted Red-Pepper Spread.
Preheat oven to 350 degrees. Coat an 8-by-4-inch loaf pan with cooking spray. Into a large bowl, sift together flours, salt, cream of tartar, baking soda, and baking powder. Stir in the nuts, sunflower seeds, oats, and bran. In a separate bowl, whisk together milk and yogurt, then stir into flour mixture just until combined.
Spoon the batter into prepared pan, and smooth the top with the back of the spoon. Sprinkle remaining 3 tablespoons sunflower seeds evenly over the top.
Bake until golden on top and pulling away from pan, about 1 hour 10 minutes. Remove from oven; immediately invert onto a wire rack to remove pan. Reinvert; let cool completely before slicing.
To store, wrap loaf tightly in plastic, and refrigerate for up to one week or freeze for up to two months.