In a large bowl, stir sugar into warm water. Sprinkle yeast on top and let sit for 5–10 minutes until it foams.

Add softened butter and salt. Stir in 3 cups of flour and mix until smooth.

Add the remaining flour ½ cup at a time, mixing until dough pulls away from the sides and forms a soft ball.

Turn dough onto a floured surface and knead for 8–10 minutes until smooth and springy.

Place in a greased bowl, cover with a clean towel, and let rise in a warm spot for about 1 hour, or until doubled.

Punch down dough, divide in two, and shape into loaves. Place each in a greased 9×5-inch loaf pan.

Cover and let rise again for 30–45 minutes, until dough domes slightly above the edge of the pans.

Bake at 375°F (190°C) for 30–35 minutes until tops are golden and loaves sound hollow when tapped.

Brush tops with butter if desired. Let cool on wire racks before slicing.