Preheat your oven to 350°F (175°C). Lightly grease and flour (or spray with cooking spray) a 9x13 inch baking dish.

Prepare the yellow cake mix according to the package directions in a large mixing bowl. Pour the batter evenly into the prepared baking dish.

Bake for 30-35 minutes, or until a wooden skewer inserted into the center comes out clean. While the cake is baking, prepare the cinnamon swirl filling and cream cheese glaze.

In a small saucepan, melt the 1/2 cup unsalted butter over medium heat. Remove from heat and stir in the packed light brown sugar, ground cinnamon, 1/4 cup heavy cream (or milk), and 1 tsp vanilla extract. Whisk until smooth and well combined.

In a medium mixing bowl, using an electric mixer, beat the softened cream cheese and 1/2 cup softened unsalted butter together until smooth and creamy, about 2-3 minutes.

Gradually add the powdered sugar, mixing until fully incorporated. Beat in the 1 tsp vanilla extract. Add 2 tablespoons of milk (or heavy cream) and beat until the glaze is smooth and pourable, yet thick enough to coat a spoon. Add an additional tablespoon of milk if needed to reach your desired consistency.

Once the cake is out of the oven, let it cool in the pan for 5-10 minutes. While still warm, use the handle of a wooden spoon or a dowel to poke holes evenly all over the top of the cake, about 1 inch apart. Don't go all the way to the bottom of the pan.

Pour the warm cinnamon swirl filling evenly over the top of the cake, ensuring it seeps into all the poked holes. Use a spatula to gently spread any excess over the surface.

Allow the cake to cool completely at room temperature, about 1-2 hours, before frosting. This ensures the glaze won't melt.

Once completely cooled, spread the cream cheese glaze evenly over the top of the cake. If desired, sprinkle with extra ground cinnamon or chopped pecans.

Chill the cake in the refrigerator for at least 30 minutes before slicing and serving. This helps the glaze set and makes for cleaner slices.