Combine vinegar, honey, salt, poppyseeds, and dried onion in a blender.
Keeping blender going on high, drizzle oil slowly into blender allowing ingredients to emulsify. It should become opaque and creamy.
When oil is completely added blend for a few seconds more and then turn off.
Use dressing as desired. Store in fridge.
Makes approximately 3/4 cup. Double, triple as desired.