1. Combine vinegar, honey, thyme, and garlic in small bowl; set aside.

2. Adjust oven rack to middle position; heat oven to 450°F. Line rimmed baking sheet with aluminum foil; spread beans and onion wedges on baking sheet. Drizzle with oil; using hands, toss to coat evenly. Sprinkle with 1/2 teaspoon salt, toss to coat, and distribute in even layer. Roast 10 minutes.

3. Remove baking sheet from oven. Using tongs, coat beans and onion evenly with vinegar/honey mixture; redistribute in even layer. Continue roasting until onions and beans are dark golden brown in spots and beans have started to shrivel, 10 to 12 minutes longer.

4. Adjust seasoning with salt and pepper and toss well to combine. Transfer to serving dish, sprinkle with walnuts, and serve.

Serves 4