In a large skillet over medium heat, heat the oil.
Add the onion and cook for 5 minutes, stirring to
caramelize but not over brown. Add butter and
sugar and cook until onions have nicely
caramelized, about 15 minutes. Remove from heat
Once cooled mix together the remaining ingredients
except for the tortillas and vinegar; refrigerate
for at least 4 hours.
After mixture has had time to meld, set aside 1/3
of the mixture for the dipping sauce and evenly
spread the remaining mixture on the top of 11
tortillas. Make sure to spread to edges of
tortillas so tortillas completely seal to each
other. Stack the tortillas on top of one another,
with the last tortilla on top having no mixture
spread on it. Wrap tortilla stack in plastic wrap
and let set up for 12 to 24 hours in refrigerator.