Place butter into a small bowl. Stir in the garlic powder and salt.
Pour butter mixture over breadcrumbs and toss or stir gently to coat.
Pour bread out onto a large baking sheet. Spread out evenly.
Bake for 10 minutes and check for crispiness. Bake longer if needed, but check every few minutes or so. The croutons will get crunchier as they cool so take them out before they are totally crunchy.
Remove. Sprinkle with salt if desired.
Let cool before serving.
Notes
Thick-cut pumpernickel makes for the best croutons.