For the cake: In a medium bowl, whisk together the flour, cinnamon, baking powder, and salt. In another medium bowl, using an electric hand mixer on high speed, beat the sugar and eggs together until thick, about 2 minutes. Beat in the pumpkin puree. Gradually beat in the flour mixture. Pour the batter into the prepared pan and spread evenly. Bake until the cake springs back when touched, about 12 minutes. Run a thin metal spatula around the edges of the cake and immediately invert the pan onto the kitchen towel. Carefully peel off the parchment paper. Starting at the narrow end, roll up the cake and towel together into a log. Cool completely on a wire rack, about 45 minutes.