1/4 to 1/3 sm. onion
1 c. sugar
1/2 c. white vinegar
2 tsp. dry mustard
1 tsp. salt
1 1/2 c. oil

In blender, add first 3 ingredients; blend for 5 to 10 minutes until clear. Then add remaining ingredients and blend on medium for 10 minutes. Then add poppy seeds; blend again for 1/2 minute.