Step 1

Preheat the oven to 350 degrees Fahrenheit (175°C) and lightly grease an 8 x 10-inch baking dish with butter or cooking spray.

Step 2

For the crumb topping: mix the chopped nuts with the white sugar, brown sugar, melted butter, cinnamon, and salt.

Step 3

Mix thoroughly until well combined and wet. Set aside.

Step 4

For the cake: Beat the butter and sugar in a large bowl until pale and fluffy.

Step 5

Add the eggs, one at a time, and beat well after each addition.

Step 6

Add the sour cream and vanilla, and mix until smooth.

Step 7

Use a spatula to mix the flour, baking powder, baking soda, and salt into the butter-egg mixture.

Step 8

Scrape the sides and bottom of the bowl, and mix until just combined.

Step 9

Spread half of the cake batter in the bottom of the baking dish.

Step 10

Sprinkle or spoon half of the crumb topping over the cake batter.

Step 11

Next, carefully add the other half of the batter, spooning it gently onto the topping as evenly as possible.

Step 12

Finally, add the last half of the topping, sprinkling it gently over the second layer of batter.

Step 13

Bake for approximately 30 to 35 minutes, until golden brown.

Step 14

Check the cake is done by inserting a toothpick into the center. If the cake is ready, it will come out clean.

Step 15

(if the cake is not ready, bake in 5-minute intervals)

Step 16

Allow the cake to cool for 10 minutes. Then, serve warm, and enjoy!