In a medium plastic bowl, soak flour, covered loosely, overnight in the buttermilk. You can soak the flour for longer, up to 24 hours, for better rising results. (You can also use kefir or yogurt to soak the flour.)
Preheat the oven to 350°F. Transfer soaked flour into a large, nonreactive bowl. Beat in remaining ingredients, combining thoroughly.
Butter and flour a regular loaf pan. Pour bread batter in. Place pan into the oven, and bake for 1-1/2 hours, or until toothpick inserted into the center comes out clean.