Make the pecans: Place the pecans in a medium skillet and top with the maple syrup. Heat over medium low for 4 to 5 minutes, stirring often, until the syrup thickens and coats the pecans. Stir in the salt. Pour onto a sheet of parchment paper and separate. Let harden while you prepare the rest of the salad.
Make the dressing: In a liquid measuring cup with a spout or bowl, whisk together the oil, vinegar, maple syrup, Dijon, salt, and pepper.
Place the onion, apple, and pear in your serving bowl. Top with one-third of the dressing and stir to combine. If time allows, everything mingle for about 10 minutes while the pecans continue to cool (if you don't have time for this, no worries! I like to do it to soften the flavor of the onion a bit).
Add the spinach and cooled pecans. Toss to coat, then moisten with additional dressing as desired (be careful not to overdo it). Serve immediately.
Notes
Feel free to make extra pecans; they store at room temperature for up to 1 week.
TO STORE: This spinach salad is best enjoyed fresh, as the greens will wilt and the apples will start to brown after assembly. If you do have leftovers, eat them within a day; you can add fresh baby spinach to revive the salad a bit.