Preheat your oven to 350°F (175°C). Grease a 9x13-inch baking pan or line it with parchment paper.
In a large bowl, combine the 15.25 ounces Yellow cake mix, 1/2 cup Vegetable oil, 3 large Eggs, and 1 cup Sour cream. Mix until smooth and well combined.
In a small bowl, mix together 1/4 cup Granulated sugar, 1/2 cup Brown sugar, 2 teaspoons Ground cinnamon, melted 1/4 cup Butter, and 1/2 cup Optional nuts to form a crumbly topping.
Pour the cake batter into the prepared pan and spread evenly. Sprinkle the cinnamon topping evenly over the batter.
Bake in the preheated oven for 30–35 minutes, or until a toothpick inserted in the center comes out clean.
Allow the coffee cake to cool slightly before slicing. Serve warm or at room temperature with your favorite coffee.