Add the red onion, pear, pecans, and blue cheese, and toss to mix evenly.
To make the dressing, place the maple syrup, vinegar, mayonnaise, brown sugar, salt, and pepper in a blender, and blend thoroughly. With the motor running, slowly pour in the walnut oil. Blend until mixture becomes creamy, about 1 minute.
Pour over salad mixture, and toss to coat greens evenly.