Slice the bacon into one-inch pieces.
In a heavy bottom pan, cook diced bacon until crisp.
Remove the crips bacon from the pan with a slotted spoon and drain on a paper towel-lined plate.
Drain all but ¼ cup of bacon grease from the pan.
Add the onion to the pan and cook until softened, about 5 minutes.
In a medium bowl, whisk together the sugar, cornstarch, salt and pepper. Whisk in the water and apple cider vinegar.
Carefully pour the sugar/vinegar mixture into the pan.Scraping the bits off the bottom of the pan.
Bring the dressing to a simmer, whisking continually. Cook until thickened about 1 minute.
Add the bacon back into the dressing and stir to combine.
Serve warm over salad greens.
