Pre-heat oven to 450°F; line a rimmed baking sheet with aluminum foil.
Scrub and peel the sweet potatoes; slice each crosswise into ½-inch thick rounds.
In a large bowl, toss the sliced sweet potatoes with the melted butter, salt, and pepper.
Spread out the slices in an even layer on the prepared baking sheet.
Bake sweet potatoes in the pre-heated oven for 20 minutes, or until the bottoms are starting to brown.
While the sweet potatoes are baking, combine the maple syrup, brown sugar and pecans in a bowl.
When the sweet potatoes are finished baking, remove the baking tray from the oven and carefully flip the sweet potato slices.
Divide the maple syrup mixture evenly over the sweet potatoes, keeping the mixture in the center as best you can.
Return to the oven and bake for 5 minutes more or until the syrup is bubbly.