Cut bread lengthwise and crosswise without cutting through bottom crust. Insert cheese between cuts. Combine butter, onions and poppy seeds; drizzle over the bread. Wrap in foil; place on a baking sheet. Bake at 350° 5 minutes. Unwrap; bake 10 minutes longer or until cheese is melted.
A sliced loaf of this cheesy, oniony bread can be fanned out for a fun presentation.