Stir cream cheese, honey, lemon zest, vanilla, and salt in a bowl until smooth and fluffy.
Warm a large skillet over medium heat and briefly heat tortillas to make them pliable; set aside.
Spread the cream cheese mixture over one tortilla, leaving a small border around the edge.
Scatter blueberries evenly on top. Sprinkle sugar and cinnamon if using. Cover with the second tortilla and gently press.
Melt butter in the skillet. Cook the quesadilla 2–3 minutes per side until crisp and golden.
Rest 1 minute on a board, then slice into wedges and serve warm.