Preheat the oven to 350°F. In a small bowl, stir together the flaxseed and water and set aside.
In a large bowl, using a fork, mix together flours, baking powder, baking soda, salt, and caraway seeds. With a pastry blender or with 2 knives, cut in butter until mixture resembles coarse sand. Add chopped walnuts and (frozen!) raspberries; toss gently.
In a small bowl, whisk together yogurt, honey, and flaxseed + water mixture; add to flour mixture and stir gently with a wooden spoon just until flour is moistened. Do not overmix.
Turn dough onto floured surface and knead lightly about 5 times, adding additional flour if dough is too sticky.
Mound dough onto cornmeal-dusted baking stone or baking sheet. Bake at 350°F for 55 to 60 minutes or until loaf is slightly golden and sounds hollow when tapped. Cool completely before slicing.