Preheat the oven to 350 degrees. Prepare two 9-inch round cake pans with nonstick spray. Add ¼ cup of flour to each pan and dust the bottom and sides of both pans. Discard the remaining flour and set aside.

Add the flour, baking powder, baking soda and salt to a medium bowl and whisk to combine.

Add the softened butter to a mixing bowl and beat until smooth and creamy.

Add the white and brown sugar to the butter and beat for 2-3 minutes until creamy, light and fluffy.

Add the vanilla and mix to fully combine.

Add the eggs, one at a time, until fully combined.

Add ½ the flour mixture to the butter mixture and mix to combine.

Add ½ the buttermilk to the butter mixture and mix to combine.

Add the remaining flour and mix, then the remaining buttermilk and mix to fully combine.

Divide the batter evenly between the two prepared cake pans and lightly tap the pans on the counter to allow them to smooth out. Use an offset spatula to help with this if needed.

Bake the cakes for 30-35 minutes or until a toothpick inserted into the center of the cakes comes out clean.

Remove the cakes and allow them to fully cool before frosting.

Once the cakes are cool, run a knife around the inside edge of the pan and allow the cakes to fall gently into your hands.

Set one cake on a cake stand or plate. Use a serrated knife to remove the dome of the cake and flatten out the surface. Set aside.

Prepare the frosting by adding the light and dark brown sugar, butter and salt to a medium saucepan. Heat over medium while stirring as the butter and sugars melt together.

Whisk in the heavy cream and evaporated milk.

Continue to heat and bring the sauce to a simmer. Once simmering, whisk occasionally while cooking for four minutes.

Remove from heat and add the sauce to a heat-proof mixing bowl.

Beat on medium/low while slowly adding the powdered sugar. Be careful not to splatter the hot caramel sauce.

Add the vanilla and stir to combine.

Pour one cup of warm frosting onto the center of the cake that is on the cake stand. Use an offset spatula to spread the frosting evenly.

Place the second cake on the top and add the remaining frosting to the top of the cake a little at a time allowing it to slowly run off the top and down the edges. As it cools it will start to thicken and congeal.

Use your spatula or a bench scraper to scoop the frosting off the cake stand and up the sides of the cake. Continue to gently spread evenly over the top and sides of the cake.

Allow it to cool and set before serving.