1. Heat the oven to 400 degrees. Generously butter a 2-quart casserole, and set aside. Bake the potatoes until almost tender, 25 to 30 minutes. Remove potatoes from oven, and set aside until cool enough to handle. Slip off the skins. Cut the potatoes into 1 1/2-inch thick rounds, and transfer to a large bowl.

2. Add 5 tablespoons butter, 5 tablespoons brown sugar, cinnamon, and cayenne pepper; season with salt and pepper. Stir to combine; set aside.

3. Melt the remaining 2 tablespoons of butter in a medium sauté pan set over medium-high heat. Add the remaining 2 tablespoons brown sugar and the pecans. Cook, stirring occasionally, until the pecans have been coated and have caramelized, about 3 minutes.

4. Add the pecans to the sweet-potato mixture, and gently stir to combine. Transfer to he prepared casserole, and bake, stirring 2 or 3 times, until potatoes are caramelized and bubbly, 30 to 35 minutes. Serve immediately.