I found this recipe on pinterest.
It's originally called Cinnamon Roll Pumpkin Vanilla Sheet Cake but I didn't use vanilla pudding in the recipe. Instead I used Jello's seasonal flavor, Pumpkin Spice.
Cinnamon Roll Pumpkin Sheet Cake
1 box yellow cake mix
1/2 cup canola or vegetable oil
1/2 cup milk or buttermilk
3.4 ounce box Pumpkin Pie Spice Pudding Mix (or vanilla)
1/2 cup sour cream
15 ounce can pumpkin
1 stick (8 tablespoons) unsalted butter
3/4 cup packed light brown sugar
1/2 teaspoon ground cinnamon
3/4 cups powdered sugar
1/4-1/2 cup heavy cream (start w 1/4 cup and add a little more cream if needed)
1. Preheat oven to 350 degrees F. and spray a jelly roll pan with non stick cooking spray.
2. Place cake mix, eggs, oil, milk, pudding, sour cream and pumpkin into a stand or electric mixer, beating until well combined, about 1 1/2 minutes. Pour into prepared pan, spreading evenly.
3. Place butter into a microwave safe bowl and melt, about 30-40 seconds. Add brown sugar and cinnamon to bowl, mixing until combined. Drizzle mixture evenly over cake then take a knife and run it through to swirl.
4. Bake cake for 30-35 minutes, until cooked through and remove. Place powdered sugar and cream into a large bowl and mix until creamy and smooth. Drizzle over warm cake then let cool for 20 minutes before cutting into square