Heat the oven to 325°F. Butter a 9-inch loaf pan and dust with cornmeal.
Beat the butter, lemon zest, and all but 1 tablespoon of the sugar in a bowl until light and fluffy, about 10 minutes. Beat in the egg yolks one at time. Add the almond and vanilla extracts, soda, and sour cream and mix. Mix in 1 cup of the cornmeal, the flour and salt.
Whip the whites until stiff but not dry and fold into the batter.
Bake until a thin skewer stuck in the center comes out clean, about 1½ hours. Cool on a rack for 15 minutes and then unmold the cake.
Whip the cream, remaining 1 tablespoon sugar, and Madeira together until soft peaks form. Serve with slices of the warm pound cake.