Dissolve yeast in warm water with a little bit of sugar in a large bowl.

Mix in whole wheat flour, nonfat dry milk powder, grated lemon rind (optional), and salt.

Add water and all-purpose flour 1 cup at a time until dough is easy to handle.

Turn dough onto a lightly floured surface and knead until smooth and elastic (about 10 min).

Spray a large bowl with non-stick cooking spray.

Place dough in bowl and turn greased side up.

Cover and let rise in a warm place until doubled (about 1 1/2 hrs).

Spray a round cake pan with non-stick cooking spray.

Punch down dough.

Shape into a round, slightly flattened loaf.

Place in pan, cover and let rise until doubled (about 40 mins).

Heat oven to 375 degrees.

Bake until golden and sounds hollow when tapped (about 35 min).

Remove from pan and cool on wire rack.