Preheat oven to 350°F. In a mixer, cream together butter and sugar. Add eggs to the mixture, one at a time, beating well after each addition.
In a separate bowl, whisk together the flour, baking soda, baking powder and salt.
Add the dry ingredients to the creamed mixture. Then add the sour cream and vanilla. Mix until combined.
Pour half of the batter into a greased 8 x 8 inch pan, and sprinkle with half of the topping, distributing evenly around the surface. Add the remainder of the batter on top, and sprinkle with the remaining topping. Bake for 40-45 minutes, until a toothpick inserted in the middle of the cake comes out clean.
Notes
If you really like crumble topping I recommend doubling the amount of the ingredients. The photos in the post show what the cake looks like with double the amount which I divide for the topping and the inside layer. If you prefer less topping, just make the crumble topping as it's written in the recipe.Recipe adapted from Gimme Some Oven
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.