Step 1: To make the Crumb Topping: In a medium bowl, combine the cold butter cubes, 1 cup granulated sugar, light brown sugar, 2 1/4 cups all-purpose flour, and ground cinnamon.
Step 2: Using your fingertips, a pastry blender, or a fork, work the butter into the dry ingredients until coarse, varied-sized crumbs form. Set aside.
Step 3: To make the Coffee Cake: Preheat your oven to 350°F (175°C). Grease and flour a 9×13 inch baking pan.
Step 4: In a large bowl, cream together the softened butter and 1 1/2 cups granulated sugar until light and fluffy, about 3-5 minutes.
Step 5: Beat in the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Step 6: In a separate medium bowl, whisk together the remaining 2 1/2 cups all-purpose flour, baking soda, baking powder, and salt.
Step 7: Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream, beginning and ending with the dry ingredients. Mix until just combined, being careful not to overmix.
Step 8: Pour half of the coffee cake batter into the prepared baking pan and spread evenly.
Step 9: Sprinkle half of the crumb topping over the batter.
Step 10: Carefully spread the remaining batter over the crumb topping.
Step 11: Generously sprinkle the remaining crumb topping over the top of the cake batter.
Step 12: Bake for 40-50 minutes, or until a wooden skewer inserted into the center comes out with moist crumbs (not wet batter).
Step 13: Let the coffee cake cool in the pan on a wire rack for at least 20-30 minutes before slicing and serving.