Preheat the oven to 350F then line a 9x13 inch baking sheet with parchment and set aside. If you want a thicker coffee cake use a 9x9 inch pan.
Take ⅔ cup of the cake mix and place it in a large bowl. Add the cold cubed butter, brown sugar, cinnamon, vanilla extract, salt, and nuts. Mix well and set aside in the fridge.
¼ cup butter, ½ teaspoon salt, 1 cup light brown sugar, 1 teaspoon cinnamon, ½ teaspoon vanilla extract, ½ cup pecans, 1 box yellow cake mix
In another bowl combine the rest of the cake mix with the eggs, vanilla extract, oil, and sour cream or Greek yogurt and mix until combined.
3 eggs, 1 cup sour cream, ¼ cup vegetable oil
Pour the cake batter into the prepared pan, and spread it into an even layer. Top with the streusel topping and place in the oven.
For the 9x13-inch bake for 27-30 minutes. For the 9x9-inch bake for about 35-40 minutes or until a toothpick inserted in the center comes out clean.
Allow the cake to cool down then slice into individual slices and enjoy with your morning coffee.