Process
Preheat the oven to 450ºF and also anoint a 13" × 9" × 2" baking dish. Take a small skillet and melt butter in it. As the butter melts, add onion and celery, sauté until onion becomes tender for about 3 minutes, and set aside. In a large mixing bowl, mix bread, onions, celery, sage, black pepper, and cornbread.