In a large bowl, combine warm water, yeast, and sugar. Let sit for 5 minutes until foamy.
Add flour and salt to the yeast mixture. Stir with a wooden spoon until a shaggy dough forms. Cover bowl with plastic wrap and let rise at room temperature for 2 hours until doubled in size.
Grease two 1-quart oven-safe bowls with butter. Divide dough in half and place each half into a prepared bowl. Let rise for 30 minutes.
Preheat oven to 425°F. Brush tops of loaves with melted butter.
Bake for 15 minutes, then reduce heat to 375°F and bake for an additional 30 minutes until golden brown and bread sounds hollow when tapped.
Remove from bowls and cool on a wire rack for at least 10 minutes before slicing.