Preheat oven to 375°F (190°C). Grease a 9×13-inch baking dish.

Arrange sweet potato slices evenly in the dish.

In a saucepan, melt butter over medium heat. Stir in brown sugar, water, cinnamon, nutmeg, vanilla, and salt.

Let it come to a gentle boil, then reduce heat and simmer for 2–3 minutes.

Pour the sauce evenly over the sweet potatoes.

Cover the dish with foil and bake for 30 minutes.

Remove foil, gently stir the potatoes, and bake uncovered for another 20–25 minutes until tender and glossy.

Let them cool slightly before serving. The sauce will thicken beautifully!