Roasted Asparagus and Red Onion Quesadillas without juice

4 slices bacon , cut into 1/4-inch wide strips 1 large red onion , halved and sliced thin 2 tablespoons balsamic vinegar 1 tablespoon maple syrup 1 tablespoon[...]

1 lb asparagus , trimmed and cut into 1/2-inch-thick slices 3 tablespoons olive oil 1 large red onion , cut crosswise into 1/4-inch-thick slices and separated[...]