Step 1: Prepare the oven and pan

Preheat the oven to 325°F (163°C).

Lightly coat a 9×13-inch baking pan with nonstick cooking spray and set it aside.

Step 2: Combine the cake ingredients

In the bowl of a stand mixer, combine the yellow cake mix, pumpkin pie spice, eggs, pumpkin puree, ½ cup milk, oil, and vanilla extract.

Mix on low speed for 30 seconds.

Step 3: Beat the batter

Increase the mixer speed to medium and continue mixing for 2 minutes.

Stop as necessary to scrape down the sides and bottom of the bowl so the ingredients are evenly incorporated.

Step 4: Fill the pan

Spread the batter evenly into the prepared 9×13-inch pan, smoothing the surface gently.

Step 5: Make the cinnamon-sugar mixture

In a medium bowl, whisk together the light brown sugar and ground cinnamon until evenly combined.

Sprinkle the mixture evenly over the top of the cake batter.

Step 6: Create the cinnamon swirl

Using a butter knife, gently swirl the brown sugar and cinnamon into the cake batter.

Do not over-swirl. The goal is to create distinct cinnamon-sugar ribbons rather than completely mixing the topping into the pumpkin batter.

Step 7: Bake

Bake the Easy Pumpkin Cinnamon Roll Cake for 35–40 minutes, or until a toothpick inserted into the center comes out clean or with only a few moist crumbs.

Step 8: Cool slightly

Remove the cake from the oven and let it cool in the pan for 15–20 minutes.

The cake should still be slightly warm when you add the icing.

Step 9: Make the icing

Place the powdered sugar in a medium bowl. Add 3 tablespoons milk and whisk until smooth and pourable.

Step 10: Ice the cake

Pour the icing evenly over the slightly warm cake.

Allow the icing to set before slicing, or serve the cake while it is still warm for an especially soft, gooey dessert.