1/2 c. vinegar
1/2 c. water
1/2 c. oil (olive, corn or vegetable)
2/3 c. sugar
3 or 4 tbsp. dry mustard
1 tsp. fresh chopped onion
2 tsp. salt

NOTE: When adding the dry mustard, you may want to add just a little and sample. If it's not too spicy to your taste, add the rest.

Mix ingredients well in a blender. Serve over tossed salad.