Brush the tortillas on both sides with vegetable oil and lightly salt. Heat a large saute pan over medium heat and cook the tortillas, 1 at a time, until slightly golden on both sides. Meanwhile, in a small bowl, mix together the sour cream, lime zest and juice, cumin, and salt and pepper, to taste, until smooth. Pour into a plastic squeeze bottle or sturdy resealable plastic bag and cut small tip in corner.
Arrange the browned tortillas on a baking sheet and sprinkle evenly with cheese. (You may need to do this in batches if both tortillas don't fit on 1 tray.) Broil until the cheese bubbles and begins to brown, about for 1 to 2 minutes, (be careful not to burn). Slice each quesadilla into 8 wedges and drizzle sour cream decoratively over the top. Sprinkle with cilantro and serve.