1 med. onion, quartered
1 c. vegetable oil
1/3 c. catsup
1/3 c. vinegar
3/4 c. sugar
1/4 tsp. salt
1 tsp. Worcestershire sauce

Put all ingredients in a blender and blend on high for 1 or 2 minutes. Store in refrigerator. This is great on fresh spinach salad or on tossed salad.