Heat the oven to 375°F. Pierce the sweet potato several times with the tines of a fork. Place the sweet potato inside a loose nest of foil. Bake until tender when pierced with the tip of a paring knife, 40 to 50 minutes. Remove them from the oven and let them cool enough to handle.
Open the sweet potato across the top, pushing the flesh slightly so it rises out of the skin. Spoon on the yogurt, then the syrup. Sprinkle with nuts, and serve.
Make-Ahead Tip: One or more sweet potatoes can be cooked ahead of time and kept refrigerated for about 5 days. To warm, place it in a microwave on medium-high for one minute or in a toaster oven for 5 minutes.