Preheat oven to 400. Arrange bread slices in single later on a cookie sheet. Bake 15 minutes or lightly browned, turning slices once half way through.
Meanwhile, in a skillet melt butter and combine pepper (if using), onion, garlic, sugar, salt, oregano and pepper until vegetables are tender, about 10 minutes, stirring occasionally. Remove skillet from heat.
Remove bread slices from oven and cut bread into 1 inch cubes.
Grease 9 x 13 baking dish. Place bread cubes in dish. Spoon half of green pepper/onion mixture over bread cubes. Arranging overlapping rows of tomatoes and cheese over greenpepper mixture. Spoon remaining green pepper/onion mixture on top.
Cover dish with foil and bake for 10 minutes at 400. Uncover. bake 5 minutes longer or until hot and cheese is melted.