San Diego Cheese Steak Sandwich

San Diego Cheese Steak Sandwich (for four):

1 French baguette, cut in four pieces, and sliced through lengthwise
16 ounces (or more) thinly sliced deli roast beef
1 jar jalapeño cheese dip
1 sweet onion, sliced

Butter the bread and toast it on a griddle or in a dry frying pan. Assemble the sandwich by spreading mayo on the toasted bread, layering meat on one side and onion and cheese dip on the other.