Preheat oven to 350°F. Grease bottom and 1/2 inch up the sides of two 9x5x3-inch or four 7-1/2x3-1/2x2-inch loaf pans; set aside. In a medium bowl combine flour, baking soda, baking powder and salt; set aside.
In a large mixing bowl beat 2 cups sugar and shortening until combined. Add eggs and vanilla; beat just until combined. Beginning and ending with buttermilk, alternately add buttermilk and flour mixture to the egg mixture.
In a small bowl combine the 1/2 cup sugar and cinnamon.
Spoon half the batter into the prepared pans. Sprinkle with half the cinnamon-sugar. Spoon in remaining batter, sprinkle with remaining cinnamon-sugar mixture. To marble the batter and cinnamon-sugar, use a thin metal spatula or table knife to cut through batter, pulling up in a circular motion.
Bake bread for 40 to 50 minutes, depending on the size of loaf pans, or until a wooden toothpick inserted near the center comes out clean. Cool in pans on a wire rack for 10 minutes. Remove from pans. Cool completely.