How to make the topping
Use your fingers to press the brown sugar, granulated sugar, flour, butter and cinnamon together. Mix together until the mixture looks like wet sand and then pour in the pecan nuts.
1. Place the oven rack in the middle oven slot.
2. Preheat the oven to 350˚F (180˚C).
3. Grease your two 9-inch cake pans with butter or oil.
4. In a large bowl whisk together flour, baking powder, baking soda, cinnamon and salt.
5. In a second bowl whisk together the sour cream, brown sugar, granulated sugar, eggs, and melted butter until smooth.
6. Fold the egg mixture into the flour mix gently, until the batter is smooth.
7. Pour the batter into the two greased pans and smooth the top.
8. Sprinkle the topping over the batter.
9. Tap the pans gently on the counter to settle the batter.
10. Bake the cakes for 25 to 30 minutes, rotating the pans at the half-time mark.
11. The cakes are ready when the tops are golden. Insert a toothpick to see if crumbs come out.
12. Let the cake cool for half an hour and serve at room temperature.