Preheat oven to 350°F. Grease and flour cake pans.
In a bowl, whisk flour, baking powder, soda, and salt.
Beat butter and sugar until fluffy. Add eggs one at a time.
Mix in vanilla. Gradually add flour mixture with buttermilk.
Pour batter evenly into cake pans.
Bake for 30-35 minutes. Cool on wire rack.
In saucepan, melt butter and brown sugar.
Stir in milk. Boil for 2 minutes. Remove from heat.
Add powdered sugar. Beat until smooth.
Frost cooled cakes with caramel frosting.
Sprinkle crushed toffee and pecans on top.
Chill cake before serving.