In a large bowl, beat butter with an electric mixer until creamy.
Sift powdered sugar; gradually add to butter, beating until mixture is light and fluffy.
Beat in eggs, 1 at a time, beating well after each addition.
Beat in vanilla.
Gradually beat flour into creamed mixture.
Heavily butter a 10-inch (12-cup) plain or decorative tube pan; add sliced almonds (if used), then tilt pan to coat inside surfaces with nuts or butter pan and dust with flour.
Scrape batter into pan and smooth top surface.
Bake in a 300° oven until a slender wooden pick inserted in center comes out clean, about 1 1/2 hours.
Let cool in pan on a rack for 5 minutes; run a knife around edges of tube to loosen center of cake, then turn out onto rack to cool