In a large bowl, combine 3 cups very hot tap water with butter, sugar, and salt. Stir until butter melts; let cool until warm (110° to 115°). Stir in yeast; cover and set in a warm place until bubbly, about 15 minutes.
Add 5 cups of the flour. Beat with a heavy-duty mixer or spoon just until batter is stretchy, 2 to 5 minutes. Mix in enough of the remaining flour, about 3 1/2 cups, to form a stiff dough.
To knead with a dough hook, beat on medium speed until dough pulls from side of bowl and no longer feels sticky, about 5 minutes. If required, add more flour, 1 tablespoon at a time.
To knead by hand, scrape dough out onto a floured board and knead until smooth, about 10 minutes, adding flour as required to prevent sticking. Rinse bowl and rub with oil. Return dough to bowl and turn over to coat with oil.
Cover bowl with plastic wrap and let dough rise in a warm place until doubled, about 1 1/2 hours.
Meanwhile, if using a 5-quart cast-iron Dutch oven, cut a circle of foil to fit bottom of pan; put foil in pan. Rub the foil and sides of pan generously with salad oil. A nonstick pan that is not worn needs no preparation.
Knead dough with dough hook or on a floured board to expel air, then form into a smooth ball.
Place dough in baking pan. Cover loosely with plastic wrap and let rise in a warm place until almost doubled again, 45 minutes to 1 hour; watch closely so it doesn't rise too much.
Bake, uncovered, in a 350° oven until loaf is golden brown and sounds hollow when tapped, 50 to 55 minutes.
Remove bread from oven and invert onto a rack (you'll need a helper); remove foil and turn loaf right side up. Cool at least 45 minutes. Serve warm or cool, cut into wedges.
Nutritional analysis per ounce.