Lemon Yum Yum

Preheat oven to 350°. In 13 x 9 x 2 pan, melt butter on top of stove. Add flour, brown sugar and pecans. Spread in pan. Bake 15 minutes or until brown. While crust is cooling, in large bowl, put softened cream cheese, sugar and 1/2 large Cool Whip and vanilla. Mix with mixer. When crust is cool, add cream cheese mixture. Then top cream cheese with lemon pie filling. Then add other half of large Cool Whip. Refrigerate before serving.