Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish. In a large mixing bowl, combine the yellow cake mix, 1 egg, melted butter, 1 cup of pumpkin puree, and 1 teaspoon of vanilla extract. Mix until the batter is smooth and well combined, then spread it evenly in the prepared baking dish.

In a separate bowl, beat 8 ounces of softened cream cheese with a mixer until fluffy and smooth. Gradually add 2 eggs, 1 teaspoon of vanilla, and the remaining 1/2 cup of pumpkin puree, followed by 1/2 cup of melted butter, and the spices. Once creamy, mix in 4 cups of powdered sugar until smooth and well blended.

Pour the pumpkin filling over the cake base, ensuring it spreads evenly across the top. Bake for 40-45 minutes; the edges should be set with a slight jiggle in the center for a gooey texture. Allow to cool completely in the pan.

To make the cream cheese frosting, beat together 8 ounces of softened cream cheese, 1/4 cup of softened butter, and 1/4 cup of brown sugar until light and fluffy. Gradually add the remaining powdered sugar until creamy and smooth, then stir in 1 teaspoon of vanilla extract.

Once cooled, spread the cream cheese frosting over the entire surface of the cake. Optionally sprinkle with cinnamon or chopped pecans before serving.