Poppy Seed Dressing

1 1/4 Tbsp poppy seeds
3/4 cup vinegar (white or cider)
1/2 cup sugar
1 1/2 Tbsp grated onion
1 1/2 tsp salt
3/4 tsp dry mustard
1 1/4 cup vegetable oil

Blend all ingredients in a blender and refrigerate.