Preheat oven to 425 degrees. Line a small rimmed baking sheet with foil and set aside.

Slice the bottoms off of the sweet potatoes so they lay flat on your cutting board. Using a very sharp knife, carefully slice the sweet potatoes in about 1/8" slices, stopping about 1/4-1/2" from the bottom. It's important not to cut through to the bottom to ensure that the sweet potato stays intact.

Combine the melted butter, rosemary, salt and pepper in a small bowl, then brush the tops of the sweet potatoes as well as between the layers with half of the butter mixture.

Bake in the oven for 45-60 minutes until tender, removing from the oven halfway through the cooking time to fan the slices a bit to separate them and brush with the remaining butter mixture. Remove from heat and serve warm as-is or with your favorite toppings. Enjoy!