Mix the flour, salt and sugar in a bowl.
Stir the water into the yeast and add to the bowl.
Blend with a spatula for 2 minutes and add the diced onions. Mix again until you have a smooth dough and finish by kneading with a rolling pin.
Shape the dough into a ball, put it back in the bowl and cover with a cloth. Leave to rest for 60 minutes in a warm place.
Take the ball of dough, divide it into 2 equal pieces and leave to rest, covered, for 10 minutes. Shape into 2 loaves, place them on a baking sheet and leave to rest, covered, for 90 minutes.
With the aid of a knife, make a cross on the tops of the loaves to enable the dough to rise properly.
Put the loaves in an oven pre-heated to 220°C and bake for 30 minutes.