Preheat oven to 300°. Beat butter in a large bowl with a mixer until creamy. Slowly add powdered sugar, beating until mixture is light and fluffy. Beat in eggs, one at a time, beating well after each addition. Beat in vanilla. Gradually beat flour into creamed mixture.
Heavily butter and flour a 10-in. (12-cup) plain or decorative tube pan; add almonds, then tilt pan to coat inside with nuts. Scrape batter into pan and smooth top.
Bake until a toothpick inserted in center comes out clean, about 1 1/2 hours. Let cool in pan on a rack 5 minutes, then run a knife around edges of tube to loosen cake. Turn out onto rack and let cool at least 1 hour. Serve slightly warm or at room temperature, cut into thin slices.
Make ahead: Up to 2 days, airtight at room temperature.