New York-Style Crumb Cake

This can be made one day ahead. Cool completely. Cover and let stand at room temperature.

Ingredients for topping:
1 cup (packed) dark brown sugar
1/2 cup granulated sugar
1 1/2 T ground cinnamon
1/2 teaspoon salt
1 cup (2 sticks) unsalted butter, melted, warm
2 1/2 cups all purpose flour

Ingredients for cake:
2 1/2 cups all purpose flour
1 teaspoon baking soda
3/4 teaspoon baking powder
1/2 teaspoon salt
3/4 cup (1 1/2 sticks) unsalted butter, room temperature
1 1/2 cups granulated sugar
2 large eggs
1 1/3 cups sour cream
1 teaspoon vanila extract

Preparing the topping:
Mix both sugars, cinnamon, and salt in medium bowl and whisk to blend. Add warm melted butter and stir to blend. Add flour and toss with fork until moist clumps form (topping mixture will look slightly wet). Set aside.

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Preparing the cake:
Position rack in center of oven and preheat to 350 degrees F. Butter 13- by 9- by 2-inch glass baking dish. Sift flour, baking soda, baking powder and salt into medium bowl. Using electric mixer, beat room-temperature butter in large bowl until smooth. Add sugar and beat until light and fluffy. Add eggs 1 at a time, beating until well blended after each addition. Add sour cream and vanilla extract and beat just until blended. Add flour mixture in 3 additions, beating just until incorporated after each addition. Transfer cake batter to prepared baking dish; spread batter evenly with rubber spatula or offset spatula. Squeeze small handsful of topping together to form small clumps. Drop topping clumps evenly over cake batter, covering completely (topping will be thick).

Bake cake until tester inserted into center comes out clean and topping is deep golden brown and slightly crisp, about 1 hour. Cool cake in dish on rack at least 30 minutes. Serve slightly warm or at room temperature.