How to Make It
Bring the stock to a boil in a medium saucepan. Whisk in the amaranth, reduce heat to low, cover, and simmer for 25 minutes or until the liquid is absorbed and the amaranth is tender, stirring occasionally. Remove from the heat, stir in the butter and cheese and season to taste with salt and pepper. Pour into a greased 9-by-9-inch baking pan and cool completely. Refrigerate for at least two hours (preferably overnight) to set the “polenta."
Meanwhile, in a large saucepan, heat the oil over moderate heat. Sweat the onion, garlic and red pepper flakes for five minutes. Add the tomatoes and tomato juice, reduce the heat and simmer for 20 minutes. Keep warm.
Preheat the oven to 450º. Brush the top of the polenta with olive oil, season with salt and pepper, and bake for 45 minutes, or until the top is golden brown. Serve the polenta with the tomato sauce and garnish with cheese.