I like to pan fry my quesadillas rather than microwave so they get a bit crispy on the outside.
Heat a skillet over medium heat. Butter one side of a tortilla and lay it butter side down. Sprinkle grated cheese (Cheddar, Jack, Colby or a Mexican blend) to lightly cover.
Spread butter on one side of another tortilla and place it butter side UP. Cook a few minutes, till lightly browned on the bottom, then gently flip over with a spatula.
When the cheese is all melted, put it on a cutting board and cut into wedges.
Want less? Butter a single tortilla, start it cooking, spread the grated cheese over half the tortilla, then fold the tortilla in half. Flip when browned on one side, cook a few more minutes, slide out onto a cutting board and cut into wedges.
For a breakfast quesadilla, add applesauce and sprinkle with cinnamon, then add the cheese.