Preheat the oven to 375 degrees. Mix the cornmeal and boiling water. Let stand until cool. Dissolve the yeast in the warm (105 degrees to 115 degrees) water in a large bowl. Let stand until the yeast foams (about 5 minutes)
Add the molasses, butter, salt and the cooled cornmeal mixture. Stir in half the flour. Beat well. Add more flour, beating until dough is stiff. Cover. Let stand 15 minutes.
Turn the dough out onto a floured board. Knead 5 minutes until smooth and elastic. Clean and grease the bowl. Add the dough to the bowl and cover. Let rise until doubled (about 1 hour)
Bake until golden and loaf sounds hollow when tapped (30 to 35 minutes). Remove from pan and brush the top with melted butter while the loaf is still hot. Let cool on a rack.