In a skillet over medium-high heat, melt 2 tsp. butter (or warm olive oil) and then add the sliced onions. Sauté onions until lightly browned, 3-4 minutes, then reduce heat to medium-low, add salt and cover. Let simmer 10-15 minutes, stirring occasionally. In a large skillet or griddle over medium heat, melt butter (or warm olive oil) then add slices of Pane Turano. Sprinkle cheese evenly over all slices of bread then top with onions, turkey, peppers and barbecue sauce. Combine bread slices and continue to grill until bread is crisp and inside is warm.