Preheat oven to 400 degrees. Toss yams with 2 tbsp olive oil in a bowl. Season to taste with salt and pepper, and arrange evenly on baking sheet.
Bake in oven until yams are tender, 20-25 minutes. Cool to room temp in the refrigerator.
Meanwhile, heat remaining 1 tbsp olive oil in large skillet over medium heat. Cook and stir onion and garlic until onion caramelizes to golden brown, about 15 minutes. Stir in kale, cook until wilted and tender. Transfer kale mixture to bowl and cool to room temp in refrigerator.
Once all ingredients have cooled, combine yams, kale, red wine vinegar, and fresh thyme in bowl. Season to taste with salt and pepper, gently stir to combine.
Recipe and photo courtesy of allrecipes.com.