In a small bowl, combine the warm water and active dry yeast. Stir gently and let it sit for 5 to 10 minutes until the mixture is foamy.
In a large mixing bowl, whisk together the warmed buttermilk, granulated sugar, salt, and melted butter until combined.
Add the foamy yeast mixture to the buttermilk mixture and stir to combine.
Gradually add 3 cups of the all-purpose flour to the wet ingredients, stirring with a wooden spoon until a sticky dough forms.
Turn the dough out onto a lightly floured surface. Knead the dough, adding the remaining flour a little at a time, until the dough is smooth, elastic, and slightly tacky, about 8 to 10 minutes.
Place the dough in a lightly greased large bowl. Cover the bowl with a clean kitchen towel or plastic wrap and let it rise in a warm, draft-free area until doubled in size, about 1 hour.
Punch down the dough to release the air. Turn it out onto a lightly floured surface and shape it into a loaf.
Place the shaped dough into a greased 9×5-inch loaf pan. Cover it again and let it rise until it has doubled in size, about 30 to 40 minutes.
Preheat the oven to 375°F (190°C).
Bake the bread in the preheated oven for 30 to 35 minutes, or until the top is golden brown and the loaf sounds hollow when tapped.
Remove the bread from the oven and let it cool in the pan for 10 minutes.
Transfer the bread to a wire rack to cool completely before slicing.