Toss Potatoes in 1 TBS Olive Oil and Thyme. Season with some salt and pepper. Roast in a 375 degree oven for about 30-40 minutes, or until potatoes are tender. Remove from oven and slice into flat pieces when cooled.
In a large saute pan, heat 1 TBS oil over medium heat-high heat. Add onions and season with salt and pepper. Cook until they caramelize, about 8-10 minutes, stirring often. Add the garlic and vinegar. Cook for about 1 more minute. Remove from heat.
Mix together the sour cream sauce ingredients.
Make 4 Quesadillas by layering the cheese, onions, and potatoes on 4 tortillas. Top with the remaining 4 tortillas. Press.
Heat remaining 1 TBS oil in a non-stick skillet to medium high. Carefully cook each quesadilla for about 1-2 minutes on each side. You will know it is done when the cheese is oozing out and the tortilla is browned and crisp on the outside. Repeat the process, 1 TBS of oil per quesadilla.