Brush the tortillas on both sides with 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, being careful not to burn.
Slice each quesadilla into 8 wedges and drizzle sour cream decoratively over the top.