Melt half the butter in a large skillet over medium heat.

Place one tortilla in the skillet.

Sprinkle half the cheese over one half of the tortilla.

Fold the tortilla over the cheese.

Cook for 1 to 2 minutes per side, until golden and the cheese has melted.

Transfer to a cutting board. Repeat with the remaining butter, tortilla, and cheese.

Cut each quesadilla into wedges.

Serve warm with the salsa on the side for dipping.