In a large bowl, combine the apples, 3 tablespoons sugar and cinnamon; let stand for 1 hour.
In another bowl, cream butter and remaining sugar until light and fluffy. Add eggs, one at a time, beating well after each addition. Add vanilla. Combine flour and salt; gradually add to creamed mixture and beat until smooth.
Transfer to a greased 9-in. x 5-in. loaf pan. Push apple slices vertically into batter, placing them close together.
Bake at 300° for 1-1/2 to 1-3/4 hours or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pan to a wire rack. Serve warm.