Vidalia Onion Crusted Bread

2 tablespoons butter
1 large Vidalia onion, halved and sliced
1 3/4 cups all-purpose flour
4 teaspoons baking powder
1/2 teaspoon salt
1 1/2 cups milk
1 large egg, beaten
1/2 cup shredded Cheddar cheese

Topping
1/4 cup shredded Cheddar cheese
2 tablespoons reserved caramelized onion
1 tablespoon poppy seed
1 tablespoon melted butter

In a large skillet melt butter over medium heat; saut