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1
Place a rack in the center of the oven, and preheat the oven to 350u00b0 F. Lightly butter and flour a 10-inch tube pan, and shake out the excess flour. Set the pan aside.
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2
Place the butter in a large mixing bowl, and beat with an electric mixer on medium speed until creamy, 1 minute. Add the sugar, a couple of tablespoons at a time, beating on medium until light and creamy, 2 minutes. Add the egg yolks, one at a time, beating until combined. Set aside.
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3
Place the flour, baking powder, and salt in a large mixing bowl and sift to combine. Set aside. Place the egg whites in a large mixing bowl and, with clean beaters, beat on high speed until stiff peaks form, about 4 minutes. Set aside. Stir the lemon juice into the milk. Alternately add the flour mixture and milk to the butter mixture in 3 additions, beating on low speed just to combine. Beat in the hickory nuts and extracts, if desired, on low speed until combined. By hand, fold the beaten egg whites into the batter, just until combined. Turn the batter into the prepared pan, smooth the top, and place the pan in the oven.
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4
Bake the cake until it is golden brown and begins to pull away from the sides of the pan, 55 to 60 minutes. Remove the cake from the oven, and place the pan on a wire rack to cool for 20 minutes. Run a knife around the edges of the pan, give the pan a gentle shake, then invert the cake onto the rack to cool, right side up, for 30 minutes. Slice and serve.
