Preheat oven to 325 degrees. Spray a 9x13 inch baking pan with non-stick cooking spray. For streusel, in a small bowl, combine brown sugar, flour and cinnamon. Cut in butter until crumbly. Stir in pecans. Set aside.

For batter, in a large bowl, cream the butter and sugar with an electric mixer until light and fluffy. Beat in eggs, one at a time. Stir in vanilla.

In a medium bowl, combine flour, baking powder, baking soda and salt. Add flour mixture to creamed mixture, alternating with sour cream.

Spread half of batter into the prepared pan. Sprinkle with half of the streusel. Combine pumpkin, egg, sugar and pumpkin pie spice. Drop by tablespoonfuls over streusel and swirl gently into cake with a knife. Top with remaining batter and sprinkle with remaining streusel.

Bake for 45-50 minutes or until a toothpick inserted in center comes out clean.