Step 1

Preheat oven to 350°. Butter pan generously. Whisk flour, salt, and baking powder in a medium bowl. Using an electric mixer, beat 1 cup butter and shortening in a large bowl until light and fluffy, about 2 minutes. Slowly beat in sugar. Mix in eggs 1 at a time; beat until pale and fluffy. Mix in vanilla. Add dry ingredients in 3 additions, alternating with milk in 2 additions; begin and end with dry ingredients. Transfer to pan; smooth top.

Step 2

Bake until a tester inserted into center of cake comes out clean, about 1 hour 20 minutes. Let cake cool in pan for 10 minutes. Invert onto a wire rack, remove cake from pan, and let cool completely.