Melt butter in a large nonstick skillet over medium heat.
Add onion; cook for 10 minutes or until tender, stirring occasionally. Cool to room temperature; stir in poppy seeds and salt. Set aside.
Roll the dough into a 14 x 12-inch rectangle on a lightly floured surface.
Spread onion mixture lengthwise over half of rectangle. Fold dough in half lengthwise; press edges of dough firmly to seal.
Cut dough into 12 (6-inch-long) strips. Gently lift both ends of dough, and twist.
Place twisted dough strips 1 inch apart on a large baking sheet coated with cooking spray. Cover and let rise in a warm place (85), free from drafts, 40 minutes or until doubled in size.
Preheat oven to 37
Combine the milk and egg, and brush over dough.
Bake for 20 minutes or until golden.
Remove from baking sheet, and cool for 10 minutes on a wire rack.