Gather all ingredients. Preheat the oven to 350 degrees F (175 degrees C).

Butter an 8x10-inch baking dish.

Make the topping: Mix pecans, white sugar, brown sugar, melted butter, cinnamon, and salt together in a mixing bowl until thoroughly combined and all components are coated with butter, 3 to 4 minutes.

Make the cake: Whisk flour, baking powder, baking soda, and salt together in a medium bowl.

Mix sugar and butter together in a large bowl with a spatula until well blended. Whisk in eggs, one at a time, until thoroughly incorporated. Whisk in sour cream and vanilla. Gradually whisk in flour mixture until flour is just incorporated; do not overmix.

Spread 1/2 of the batter over the bottom of the prepared baking dish, then sprinkle with 1/2 of the topping. Carefully spoon remaining batter over topping, then sprinkle with remaining topping; very gently press topping into batter.

Bake in the preheated oven until a bamboo skewer inserted into the center comes out clean, 30 to 35 minutes.

Let cool slightly before serving.