Stir sugar into warm water and sprinkle with yeast.
Let stand 5 minutes or until the surface is frothy.
Stir gently to moisten any dry particles remaining on top.
Put half the flour into a large bowl.
Add yeast liquid to flour with starter dough, combining to make a dough.
On a floured surface, knead dough until smooth.
Cover and let rise in a warm place overnight.
Mix salt, pepper, cardamom and remaining flour into dough.
Knead until smooth.
Peel and finely chop onions.
Melt butter or margarine in a medium skillet.
Add half the onions; cook until lightly browned.
Drain well; knead cooked onion into dough with remaining raw onion.
Sprinkle a baking sheet with flour.
Shape dough into 3 loaves about 14 inches (35 cm) long; place on floured baking sheets.
Cover and let stand in a warm place 15 minutes.
Preheat oven to 450°F (230°C).
Brush loaves with water and sprinkle with a little additional flour.
Using a fine sharp knife, make several diagonal cuts across tops of loaves.
Bake 30 minutes or until loaves sound hollow when tapped on undersides.