3 pounds sweet potatoes, peeled and sliced 1/3-inch-thick
2/3 cup maple syrup
2 tablespoons cider vinegar
1 teaspoon kosher salt
Freshly ground black pepper, to taste
3 tablespoons salted butter, cut into small pieces, plus more for the pan
1/2 cup chopped pecans
Preheat your oven to 400°. Lightly grease a 9×13-inch baking pan and arrange the potatoes in it. In a small bowl, stir together the maple syrup, vinegar, salt, and pepper. Pour over the potatoes; then sprinkle the butter pieces evenly over all. Cover the pan with foil and bake 25 minutes.
Uncover the pan and baste the potatoes generously with the liquid. Cook, uncovered, basting thoroughly every 15 minutes, for 45 minutes longer. Sprinkle the pecans over all and baste one more time; then bake until the potatoes are shiny, glazed, and lightly browned, 15 to 20 minutes more. Serve hot.