Cream butter; gradually add brown sugar, beating until light and fluffy. Add egg yolks, one at a time, beating well after each addition.
Combine flour, baking powder, and salt; add to creamed mixture alternately with milk, beginning and ending with flour mixture. Beat well after each addition. Stir in lemon extract and pecans.
Beat egg whites (at room temperature) until stiff peaks form; fold into batter.
Pour batter into a greased 10- inch tube pan. Bake at 325° for 1 hour and 15 minutes or until cake tests done. Cool in pan 15 minutes; remove from pan, and cool completely.