Combine yeast and 1/2 cup warm water in a 1-cup measuring cup; let stand 5 minutes.
Heat milk and next 3 ingredients in a saucepan over medium heat, stirring until butter melts. Cool to 100° to 110°.
Beat yeast mixture, milk mixture, and eggs at medium speed with an electric mixer until blended. Gradually add flour, beating at lowest speed until blended. (Mixture will be a very sticky, soft dough.)
Cover and let rise in a warm place (85°), free from drafts, 1 hour or until dough is doubled in bulk.
Stir dough down; cover and let rise in a warm place (85°), free from drafts, 30 minutes or until dough is doubled in bulk.
Stir dough down, and spoon into a well-greased, 10-inch Bundt pan or tube pan. Cover and let rise in a warm place (85°), free from drafts, 20 to 30 minutes or until dough is doubled in bulk.
Bake at 350° for 35 to 40 minutes or until golden brown and a wooden pick inserted into center of bread comes out clean. Remove from pan immediately. Serve bread with Blackberry Butter, honey, molasses, or jelly, if desired.
Blackberry Butter: Stir 2 to 3 tablespoons seedless blackberry jam into 1/2 cup softened butter.