Preheat oven to 160 degrees C. Grease and flour a 25cm ring tin. Mix together the flour and baking powder; set aside.
In a large bowl, cream together the butter, brown sugar and white sugar until light and fluffy. Beat in the eggs one at a time then stir in the vanilla. Beat in the flour mixture alternately with the milk, mixing just until incorporated. Stir in the chopped pecans. Pour batter into prepared tin.
Bake in the preheated oven for 60 to 75 minutes or until a toothpick inserted into the centre of the cake comes out clean. Let cool in tin for 10 minutes, then turn out onto a wire rack and cool completely.