Cut the bread diagonally with a bread knife, making sure not to cut through the bottom of the loaf.
Cut the bread again diagonally, this time in the opposite direction. Make sure to not cut all the way through again. The second cut will give you the squares or rectangles that will be pulled out after baking.
Spoon the pizza sauce in the crevices of the cut bread, moving pieces to make sure you cover all the holes.
Next, stuff all the crevices with pepperoni slices and sliced onions.
Finally, place the cheese in the crevices of the bread, making sure to cover any open spots. You want all the crevices to be covered in cheese.
Optional glaze: melt the butter and mix in garlic powder and pour it over the top of the bread before baking.
Wrap bread in foil and bake for 10 minutes.
Remove the foil and bake for another 20 minutes or until the cheese is melted and the top is golden brown.
Remove, allow to cool slightly and serve with pizza sauce.
Notes
Please refer to my tips above for other substitutions or for the answers to the most common questions.