Combine water, yeast, and sugar in a large bowl; stand 5 minutes until foamy.
Stir in flour and salt with wooden spoon until shaggy dough forms; cover with plastic wrap and rise at room temperature 2 hours until doubled.
Butter two 1-quart oven-safe bowls; divide dough equally between them. Rise 30 minutes.
Preheat oven to 425°F; brush loaf tops with melted butter.
Bake 15 minutes; reduce oven to 375°F and bake another 30 minutes until golden brown and hollow-sounding when tapped.
Remove from bowls; cool on wire rack at least 10 minutes before slicing.