Heat oven to 375 degrees F (350 degrees F if using a dark or nonstick dish). Butter bottom and sides of a 4 to 6-cup souffle dish.

In a medium saucepan over medium heat, heat buttermilk until warm to the touch. Add cornmeal; stir 2 to 3 minutes until thickened and smooth. Remove from heat. Stir in butter and salt. Let cool slightly.

Meanwhile, beat egg whites until soft peaks form. Stir egg yolks and green onions into cornmeal mixture until well combined, then gently and carefully fold in egg whites.

Pour batter evenly into prepared dish. Bake 30 to 35 minutes until bread is set, puffy and golden brown on top. Serve immediately.