1. 1. Preheat oven to 325 degrees.

Make Classic Pound Cake Batter

1. 1. Butter two 5-by-9-inch loaf pans. Combine all-purpose flour and salt in a bowl.
2. 2. Cream butter and sugar with a mixer on high speed until pale and fluffy, for 8 minutes. Scrape down sides of bowl. Reduce speed to medium, and add vanilla extract.
3. 3. Lightly beat eggs, and add to mixer bowl in 4 additions, mixing thoroughly after each and scraping down sides. Reduce speed to low, and add flour mixture in 4 additions, mixing until just incorporated.

Make Chocolate Pound Cake Batter

1. 1. Butter two 5-by-9-inch loaf pans. Combine all-purpose flour, unsweetened cocoa powder, and salt in a bowl.
2. 2. Cream butter and sugar with a mixer on high speed until pale and fluffy, for 8 minutes. Scrape down sides of bowl. Reduce speed to medium, and add vanilla extract.
3. 3. Lightly beat eggs, and add to mixer bowl in 4 additions, mixing thoroughly after each and scraping down sides. Reduce speed to low, and add flour mixture in 4 additions, mixing until just incorporated.

Combine Batters for Chocolate Marble Pound Cake

1. 1. Scoop batters into prepared pans, 1/2 cup at a time, alternating plain and chocolate. Swirl with a knife. Tap on counter to distribute; smooth tops.
2. 2. Bake until a tester inserted into center of each cake comes out clean, about 65 minutes. Let cool in pans on a wire rack for 30 minutes. Remove from pans, and let cool completely on wire rack.