Onion juice?
From a box sold in San Antonio, Texas.
Poppy Seed Dressing
1 1/2 c. sugar
2 t. dry mustard
2 t. salt
2/3 c. vinegar
3 T. onion juice
2 c. salad oil (Wesson)
3 T. poppy seeds
In blender:
Mix sugar, mustard, salt and vinegar. Add onion juice and blend well. Put on lid and add oil slowly. Add poppy seeds and blend.