Thaw dough. Make 3 lengthwise cuts almost to bottom of loaf. Mix cheese, onion, and poppy seeds. Spread 1/3 of mixture down each slit. Press dough together to form loaf again. Place in lightly greased bread pan. Brush with melted butter. Let rise 1/2 inch above sides. Bake at 350 degrees for 25 to 30 minutes.