In a large mixing bowl, dissolve yeast and sugar in warm water. Let stand until creamy, about 10 minutes.

Stir salt, shortening, minced onions, oregano and 2 cups bread flour into yeast mixture. Stir in the remaining flour, 1/2 cup at a time, beating well after each addition. Cover with a damp cloth and let rise in a warm place until doubled in volume, about 1 hour.

Stir dough to deflate and place it into a lightly greased 9x5 inch loaf pan. Cover with a damp cloth and let rise until the top of the dough is within 1/2 inch of the top of the pan, about 40 minutes. Meanwhile, preheat oven to 375 degrees F (190 degrees C).

After loaf has risen, arrange onion slices on top of the loaf. Pour melted butter over the slices and bake in preheated oven for 35 to 40 minutes, or until golden brown. Remove from pan to cool on a wire rack.