This is great on oysters, grilled fish, chicken, and salads, or you can toss it with roasted or grilled veggies like asparagus and beets. This keeps for several days in the refrigerator. Came from The Big Sur bakery.
Pour the orange juice into a small saucepan and reduce it over medium-high heat until syrupy, 5 to 7 minutes - you should be left with about 1 tablespoon. Put the reduced orange juice, vinegar, mustard, salt, lemon juice, and lemon zest into a blender. With the blender running, add the oil in a slow, steady stream, blending until the dressing is thick and emulsified. Transfer the dressing to a plastic container or glass jar and refrigerate until ready to use.