Preheat oven to 350°F. Spray the bottom and sides of 9 inch springform pan or 9 x 9 inch square baking pan with baking spray. You can also butter and flour. Set aside.
In a medium-size mixing bowl, use a whisk to sift together flour, baking powder, baking soda and salt.
Using an electric mixer, cream together butter and sugar with vanilla. Beat for 2 minutes until creamy and combined. Add eggs one at a time beating well after each addition.
Lower speed of the mixer, adding the sifted dry ingredients alternately with the sour cream beginning and ending with flour. Beat just until fully combined, don not over beat.
Meanwhile, in a separate bowl, toss together brown sugar, flour, cinnamon, nutmeg and pecans. Toss with melted butter.
Spread one half batter in prepared pan. Sprinkle 1/2 topping over batter. Pour remaining batter on top, sprinkling the top of the cake with reserved topping.
Bake for 30 minutes, then lay foil on top. Continue to bake for another 20-30 minutes or until a toothpick inserted into the center shows moist crumbs.
Cool in the pan for 30 minutes, then remove outer ring. Cool completely on a cooling rack. (If using a 9 x 9 inch pan, cool completely in the pan.)
Store leftovers at room temperature in an airtight container.