Put the corn flour in a deep bowl, pour lukewarm water over it and mix well with a spoon. Add white fine flour, salt, baking powder and mix well. Create a well in the centre and add dry yeast, sugar, milk, melted butter and mix with a spoon.
Once all the ingredients are combined, knead the dough on a floured surface with your hand until smooth and consistent. Place the dough in a bowl, cover with a cloth and leave in a warm place for about 1 hour to rise.
Knead the dough again and shape it into a ball. Place it in a baking paper covered iron pot or baking tray with a lid, sprinkle with corn flour and let it rise some more (the longer it rises, the less compacted the bread will be). Preheat the oven to 180°C, bake for 40-50 minutes covered, then carefully remove the lid and bake for another 10 minutes.