1 (14 oz.) loaf unsliced French bread
1/2 c. mayonnaise or salad dressing
1/2 c. grated Parmesan cheese
1/4 c. finely chopped onion

Slice bread lengthwise; place on a baking sheet. Combine remaining ingredients; spread cheese mixture over cut sides of bread. Bake at 375 degrees for 15 to 18 minutes or until golden brown.