Simple. Good. 

Ingredients
1 pound sourdough, French or Italian bread
4 scallions, cut into rings
6 tablespoons unsalted butter, softened
4 tablespoons grated Parmesan cheese

Preparation
Preheat broiler. Cut bread in half lengthwise. Combine scallions, butter and cheese and spread on cut sides of bread. Toast under broiler until cheese melts and bread begins to brown.

– nytimes.com