In a large saute pan, heat the oil over medium high heat.
Add the onions and cook, stirring a few times, for about 10 minutes
Add the vinegar, sugar, salt and pepper.
Cover, and then reduce the heat to low and cook for about 3 hours, stirring every 30 minutes.
The onions are done when the liquid has evaporated, the mixture is dark and sticky, and it measures about a cup. If you still have liquid in the pan after 3 hours, just raise the temperature and cook uncovered until the liquid evaporates.
Remove from the heat and transfer to a dinner plate to cool.
Place the cooled onions in a food processor fitted with the metal blade.
Add the sour cream, yogurt and red pepper after patting it dry.
Process and smooth.
Refrigerate before serving.