Buckwheat is not wheat, but it is kind of wonderful. This cake is a close relative of the pancake and will upstage any coffee cake in proximity.  Fresh blueberries give it the sweetness of cake, while aromatic orange zest and freshly grated nutmeg rounds out the earthiness of the buckwheat.  Buttermilk results in a richness and moist texture, but light and fluffy, not like a pound cake.  This cake needs no frosting, but perhaps could stand a shake of powdered sugar on top of its auburn crust. Use fresh blueberries.  Or any berry you like, really.  But the blues are right at home with the buckwheat.  Serve with juicy orange slices and hot coffee. Blueberry-Orange Buckwheat Bundt Adapted from Kitchen Sense, by Mitchell Davis, and Orangette. 1…