Make the cinnamon sugar: Stir the brown sugar and cinnamon together in a small bowl. Set aside.

Prep the pans: Preheat oven to 350°F (175°C). Grease and flour three 8x2-inch round cake pans.

Whisk dry ingredients: In a medium bowl, whisk together cake flour, baking powder, baking soda, and salt.

Combine wet ingredients: In another bowl, mix buttermilk, vegetable oil, and vanilla extract.

Cream butter and sugar: In a large bowl, beat softened butter until smooth. Gradually add granulated sugar and beat on medium for 3-5 minutes until light and fluffy. Add eggs one at a time, mixing well after each addition.

Alternate wet and dry: With the mixer on low, add the flour mixture and buttermilk mixture in batches, starting and ending with dry ingredients. Mix just until combined.

Layer the batter: Divide a cup of batter into each cake pan. Sprinkle cinnamon sugar mixture evenly over, then cover with remaining batter and gently smooth.

Bake and cool: Bake 25-30 minutes until a toothpick comes out clean or with moist crumbs. Cool in pans 10 minutes, then turn out and cool completely on wire racks.

Make the caramel: In a medium saucepan over medium heat, melt butter. Add brown sugar, cream, vanilla, salt, and corn syrup. Bring to a boil, reduce heat, cover, and simmer for 5-6 minutes, stirring frequently. Remove from heat and let cool.

Make frosting: Beat softened butter until smooth. Add cream cheese in pieces, beating until smooth. Mix in vanilla, salt, cinnamon, and gradually add powdered sugar. Beat until fluffy.

Assemble: Place one cake layer on a plate and add frosting. Repeat layering with the other layers. Apply a thin crumb coat and freeze for 15 minutes.

Finish and decorate: Frost the chilled cake with the remaining cream cheese frosting. Chill again if using caramel drip, then drizzle cooled caramel over the edges and optionally pipe frosting rosettes to decorate.