In a large bowl, cream butter and sugar until light and fluffy. Add egg yolks, one at a time, beating well after each addition. Beat in vanilla. Combine flour and baking powder; add to creamed mixture alternately with milk, beating well after each addition. Pour into three parchment paper-lined 9-in. round baking pans; set aside.
In a large bowl, beat egg whites on medium speed until foamy. Gradually beat in sugar, 1 tablespoon at a time, on high until stiff glossy peaks form and sugar is dissolved. Add vanilla. Fold in 1/2 cup walnuts. Spread meringue evenly over cake batter; sprinkle with remaining walnuts.
Bake at 325° for 30-35 minutes or until meringue is lightly browned. Cool on wire racks for 10 minutes (meringue will crack). Loosen edges of cakes from pans with a knife. Using two large spatulas, carefully remove one cake to a serving plate, meringue side up. Carefully remove remaining cakes, meringue side up, to wire racks.
In a large bowl, beat cream until it begins to thicken. Gradually add confectioners' sugar; beat until stiff peaks form. Carefully spread half of the filling over cake on serving plate; top with half of the raspberries. Repeat layers. Top with remaining cake. Store in the refrigerator. Yield: 16-18 servings.