Chef John's coffee cake is like two coffee cakes in one. It has a sour cream coffee cake layer topped with a pecan streusel topping that is then repeated for a delicious cake with tons of crunchy, buttery crumbs.
Crumb Topping:
1 ½ cups pecans, finely chopped
⅓ cup white sugar
⅓ cup packed light brown sugar
3 tablespoons melted butter
1 teaspoon cinnamon
⅛ teaspoon salt
Cake:
1 ⅞ cups all-purpose flour
1 teaspoon baking powder
¾ teaspoon baking soda
½ teaspoon fine sea salt
1 cup white sugar
½ cup unsalted butter, softened
2 large eggs
1 cup sour cream or creme fraiche
1 ½ teaspoons vanilla extract
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.