Cut the sweet potatoes into ½ inch rounds and then quarter. (I did this in stacks of 2-3) Divide the potatoes in half between two large sheet pans. Divide the 3 Tbs of oil and salt between the pans and pepper to taste. Toss the potatoes and seasonings until coated well.
Bake for 30-35 minutes or until lightly browned and soft. Stir a few times while baking. ( I also rotated the pans halfway through)
In a medium bowl, whisk together the vinegar and mustard. Slowly drizzle in the ¼ cup oil while continuing to whisk constantly until well blended.
Place cooked potatoes and raw onions into a large bowl or serving dish.
Mix in the craisins, raisins and pecans. Pour the dressing on top and stir to coat evenly. Serve warm or cool.
*If you want more heat you can cut the onion into larger pieces or add more.