Buttermilk Breakfast Cake

This is from Southern Living. I haven't made it yet, but I can't wait to try it. I'll let you know how it turns out.

Buttermilk Breakfast Cake
1 package white cake mix
1 cup buttermilk
1/2 cup melted butter
5 large eggs
3 Tbsp light brown sugar
2 tsp. cinnamon
Shortening
1 Tbsp. sugar
Buttermilk-Vanilla Glaze

1. Preheat oven to 350 degrees. Beat first three ingredients at medium speed with an electric mixer 1-1/2 minutes or until thoroughly blended; add eggs, 1 at a time, beating well after each addition.
2. Stir together brown sugar and cinnamon in a small bowl.
3. Grease a 12-cup Bundt pan with shortening; sprinkle with 1 Tbsp sugar.
4. Spoon one-third of batter into prepared pan; sprinkle brown sugar mixture evenly over batter. Top with remaining batter.
5. Bake at 350 for 45 minutes or until a long wooden pick inserted in center of cake comes out clean. Cool cake in pan on a wire rack 15 minutes; remove from pan to wire rack, and cool 20 minutes. Drizzle glaze over slightly warm cake.

Buttermilk-Vanilla Glaze
1 cup powdered sugar
1 Tbsp melted butter
1 tsp. vanilla
1 to 2 Tbsp buttermilk

1. Stir together first 3 ingredients and 1 Tbsp buttermilk until smooth, adding additional 1 Tbsp buttermilk, if necessary, for desired consistency.