Heat the oil in a saucepan over medium-high heat. Add the onion and sauté for 2 minutes until soft. Add the jalapeños and continue cooking for an additional minute. Add the balsamic vinegar, sugar and orange zest. Cook for another 2 minutes, then add the raspberry preserves and thawed raspberries. Continue cooking until slightly thickened, 5 minutes. Season to taste with salt and pepper.
Purée the sauce using a hand-held blender, regular blender or food processor. If desired, pass through a sieve to remove the raspberry seeds. Transfer to a serving dish.