Preheat the oven to 400°F (200°C).

Clean and cut the sweet potatoes into 1/2-inch thick rounds. You can either keep the skin on or peel it based on preference.

In a large bowl (or ziplock bag), toss the sweet potato slices with the melted butter, 1 teaspoon cinnamon, salt, and pepper until fully coated.

Arrange the sweet potato slices in a single layer on a baking sheet, leaving space between each slice to allow browning. Bake for 25-30 minutes until tender. The baking time may vary based on the thickness of the slices.

While the sweet potatoes are baking, mix the maple syrup, chopped walnuts, ½ teaspoon cinnamon, and thyme in a bowl.

Remove the sweet potatoes from the oven, and top each slice with about 1 teaspoon of the walnut-maple mixture.

Return the tray to the oven and bake for an additional 8-10 minutes, or until the walnuts are toasted and the maple mixture is bubbly.

Serve warm as is, or sprinkle with feta for an extra savory touch.