In a sauté pan, heat 1 tablespoon of olive oil over medium heat and sauté onion until translucent. Salt as desired and remove from pan, allow onions to cool.
Bring 1 cup of water to a boil and pour over dried chiles in a heat proof bowl. Allow mixture to sit for at least 20 minutes. Place reconstituted chiles, garlic, shredded bread and olive oil into a food processor and pulse until a chunky spread forms. To thin out further, use additional chile water. Remove and spread on one side of sandwich bread. Will make about a cup of spread, use about 1 to 2 tablespoons per sandwich.
Layer with desired amount of cheese and onion. Heat a griddle or pan over medium heat and brush each side of bread with melted butter. Grill until golden brown and cheese is melted. Enjoy while warm.