Preheat oven to 350°F (175°C) and grease a 9-inch pan.
Mix flour, baking powder, baking soda, salt, and spices in a bowl.
In another bowl, beat together pumpkin, sugar, butter, eggs, and vanilla.
Add dry ingredients to the wet ingredients and stir to combine.
Fold in chopped pecans, then pour batter into the prepared pan.
In a small bowl, mix topping ingredients and sprinkle over the cake.
Bake for 45 minutes, or until a toothpick comes out clean.