Preheat oven to 350 degrees F (175 degrees C). Line two 9-inch round cake pans with parchment paper. Grease and flour the parchment paper.
Combine flour, cocoa powder, salt, baking soda, baking powder, and cinnamon in a bowl.
Beat sugar and shortening together in a large bowl with an electric mixer. Mix in eggs and vanilla extract until smooth. Mix in buttermilk and water. Add flour mixture slowly, beating on low speed until batter is smooth and creamy, about 3 minutes. Pour batter into the prepared pans.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, about 25 minutes. Place pans on a wire rack to cool, about 10 minutes. Invert cakes carefully onto serving plates.
Combine caramels, milk, and butter in a saucepan over low heat; cook, stirring frequently, until caramels are melted, 5 to 10 minutes. Remove from heat and cool for 3 minutes.
Sprinkle 1/2 of the pecan pieces and chocolate chips over 1 cake layer, leaving a 1/4-inch border. Pour 1/4 of the caramel on top. Place second cake layer on top. Sprinkle remaining pecans and chocolate chips over the cake. Pour remaining caramel on top, allowing some to drizzle down the sides.