Begin by preheating your oven to 350 degrees Fahrenheit (175 degrees Celsius). Prepare a 9x13-inch baking pan by lightly greasing it to prevent sticking.

In a large mixing bowl, combine the yellow cake mix, pumpkin puree, eggs, granulated sugar, vegetable oil, water, and ground cinnamon. Beat the mixture until it is well incorporated and smooth. Once blended, pour the batter into the prepared baking dish.

Place the cake in the preheated oven and bake for approximately 45 minutes, or until a toothpick inserted into the center comes out clean.