1 cup pearl onions (about ¼ pound), preferably red, peeled
4 carrots, halved lengthwise and cut into ¾-inch chunks
4 parsnips, halved lengthwise and cut into ¾-inch chunks
5½ Tbsp. extra-virgin olive oil, divided
1½ tsp. kosher salt, divided
1 tsp. dried thyme
½ tsp. ground black pepper, divided
2 Tbsp. apple cider vinegar
2 tsp. honey
1 (5-ounce) bag baby arugula
2 ripe but firm pears, cored and sliced
½ cup toasted walnuts
Active time: 20 minutes
Total time: 1 hour
Preheat oven to 375°. In a large bowl, toss onions, carrots, and parsnips with 1½ Tbsp. oil, 1 tsp. salt, thyme, and ¼ tsp. pepper. Transfer vegetables to a large rimmed baking sheet and roast, stirring occasionally, until tender and golden brown, about 40 minutes; set aside to let cool until just warm.
Meanwhile, in a large bowl, whisk together vinegar, honey, and remaining ½ tsp. salt and ¼ tsp. pepper. While continuing to whisk constantly, drizzle in remaining ¼ cup oil; set dressing aside.
Toss arugula, pears, and roasted vegetables in bowl with reserved dressing. Transfer to plates, garnish with walnuts, and serve.