Preheat oven to 425 degrees F. Line a 9x13-inch baking dish with parchment paper and spray generously with cooking spray.

Toss thinly sliced sweet potatoes with melted butter, brown sugar, and cinnamon in a large bowl. Set aside.

Whisk together water, olive oil, and eggs until well combined. Set aside.

In a large bowl, combine parmesan, cornmeal, rice flour, thyme, salt, and pepper. Stir to combine, then make a well in the center. Pour water and egg mixture and mix until well combined.

Add seasoned sweet potatoes to batter, stirring gently until combined. Pour batter into prepared baking dish and spread into an even layer. Bake sweet potato scarpaccia for 30-35 minutes or until golden brown and crispy. Remove from the oven and top with extra grated parmesan and fresh chives. Serve warm.