Grease 24, 2-1/2-inch muffin cups well; set aside. In a medium bowl, stir together flour, salt, and baking soda; set aside.

In a large bowl, beat shortening with an electric mixer on medium to high speed for 30 seconds. Gradually add the 1-1/2 cups sugar, about 1/4 cup at a time, beating on medium speed until well combined and scraping sides of bowl. Beat on medium speed for 2 minutes more. Add eggs, 1 at a time, beating after each addition. Alternately add flour mixture and buttermilk to shortening mixture, beating on low speed after each addition just until combined. Fold in apples.

Spoon batter into prepared muffin cups, filling each two-thirds full. Bake in a 350 degree F oven for 18 to 20 minutes or until dark golden brown and a wooden toothpick inserted in centers comes out clean. Donuts will dip in the middle. Cool in muffin cups on a wire rack for 15 minutes. Loosen edges of the donuts with a thin spatula to remove from muffin cups.

Meanwhile, in a small bowl, combine the 1/2 cup sugar and cinnamon. Carefully remove donuts from muffin cups; donuts will be tender. While still warm, roll donuts in the sugar mixture. Serve warm. Makes 24 donuts.