Grease and lightly flour a 9x5x3-inch loaf pan; set aside. In a medium bowl, combine flour, sugar, and baking powder. Cut in butter to resemble coarse crumbs. Set aside 1/2 cup.
Mix eggs, milk, and lemon extract; add to remaining crumb mixture along with walnuts. Stir until combined (batter will be thick). Spread in prepared pan. Top with reserved crumb mixture.
Bake in a 350 degree F oven for 55 to 60 minutes or until a wooden toothpick inserted in center comes out clean. Cool in pan on a wire rack for 10 minutes. Remove from pan; cool completely on wire rack. Makes 18 servings.