1. Pre-heat a grill or grill pan over medium high heat.
2. Slice your peach in half from pole to pole and remove the pit. Slice each half lengthwise into 1/2-inch pieces. Thread the peach slices onto metal or bamboo skewers.
3. Brush the peach skewers and onion rounds lightly with olive oil, and place them on the hot grill. Cook the peaches for about 2 minutes per side until grill marks appear and the fruit has softened slightly. Cook the onion for 3 minutes preside until slightly charred and softened.
4. Roughly chop the peaches and onions.
5. To assemble each quesadilla: sprinkle 1/4 cup cheese on one half of a tortilla. Top with a quarter of the peaches, onion, tomatoes and cilantro. Sprinkle with another 1/4 cup cheese and fold the empty half of the tortilla over the filling to close.
6. Grill the quesadillas for 3 minutes per side until the cheese is melted and the tortilla is crisp.
7. Slice each quesadilla into 3 triangles and serve immediately. Get some guacamole involved if you’re feeling festive.