Sweet Vidalia Onion Custard Bread

Source: Vidalia Onions

2 tablespoons butter or margarine
1 large Sweet 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, lightly beaten
1/2 cup shredded Cheddar cheese

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

In a large skillet, melt butter over medium heat. Saut