Preheat the oven to 180°C (356°F) and prepare your 9-inch round cake pans by greasing them with butter and lining with parchment paper.

In a large mixing bowl, cream the softened butter, caster sugar, and light brown sugar on medium speed for 4-5 minutes until pale and fluffy.

Add in the eggs one at a time, mixing well after each addition. Gradually mix in flour and baking powder until just combined.

Divide the batter between the prepared pans and bake for 25-30 minutes, checking for doneness with a toothpick.

Allow the cakes to cool in the pans for 10-15 minutes before inverting onto a wire rack to cool completely.

Make the frosting by beating the softened butter for 5 minutes until fluffy, then gradually adding the heavy cream and caramel.

Once cooled, place one cake layer on a serving plate, add frosting on top, then place the second layer on top and apply a crumb coat.

Refrigerate for 20 minutes to set the crumb coat, then frost the entire cake with a final layer of frosting.

Warm the caramel sauce slightly and drizzle around the edge of the cake, allowing it to flow down the sides.

Drizzle any remaining caramel on top and optionally sprinkle with flaky salt and any desired toppings.