Step 1: Preheat the Oven and Prepare the Cake Tins

1. Preheat your oven to 180°C (350°F).
2. Grease two 8-inch cake tins with butter or oil.
3. Line the bottoms of the tins with parchment paper to ensure the cakes release easily after baking.

Step 2: Prepare the Caramel Sauce

1. In a medium saucepan, heat 200g (1 cup) granulated sugar over medium heat.
2. Stir constantly until the sugar melts into a golden amber liquid.
3. Carefully add 90g (⅓ cup) unsalted butter and stir until melted.
4. Gradually pour in 120ml (½ cup) heavy cream while stirring continuously.
5. Remove from heat and stir in 1 tsp sea salt.
6. Allow the caramel to cool slightly before using.

Step 3: Mix the Dry Ingredients

1. In a large bowl, sift together:
   • 225g (1 ¾ cups) all-purpose flour
   • 2 tsp baking powder
   • ½ tsp salt
2. Set aside the dry mixture.

Step 4: Cream Butter and Sugar

1. Using an electric mixer, cream together:
   • 175g (¾ cup) unsalted butter
   • 175g (¾ cup) granulated sugar
2. Beat until light and fluffy, about 3-4 minutes.

Step 5: Add Eggs and Vanilla

1. Beat in the 3 large eggs, one at a time, ensuring each is fully incorporated before adding the next.
2. Mix in 2 tsp vanilla extract until well combined.

Step 6: Combine Wet and Dry Ingredients

1. Gradually add the dry ingredients to the butter mixture in three parts.
2. Alternate with 120ml (½ cup) whole milk, beginning and ending with the flour mixture.
3. Mix until just combined, being careful not to overmix.

Step 7: Incorporate Caramel Sauce

1. Gently fold in 60ml (¼ cup) of the prepared caramel sauce into the batter.
2. Create a marbled effect by swirling the caramel through the batter.

Step 8: Bake the Cakes

1. Divide the batter evenly between the prepared cake tins.
2. Bake in the preheated oven for 25-30 minutes.
3. Check doneness by inserting a toothpick into the center; it should come out clean.
4. Allow the cakes to cool in the tins for 10 minutes before transferring them to a wire rack to cool completely.

Step 9: Assemble the Cake

1. Once the cakes are completely cool, place one layer on a serving plate.
2. Spread the remaining 140ml (½ cup) caramel sauce over the top of the first layer.
3. Place the second cake layer on top and gently press down.

Step 10: Add the Salted Caramel Topping

1. Pour the remaining caramel sauce over the top of the cake, allowing it to drizzle down the sides.
2. Sprinkle with additional sea salt flakes for an extra burst of flavor.

Step 11: Serve and Enjoy

1. Slice the cake into desired portions.
2. Serve with a dollop of whipped cream or a scoop of vanilla ice cream for an extra decadent treat.