Step 1: Preheat and Prepare the Baking Pan

Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking pan and line it with parchment paper, leaving an overhang for easy removal. Lightly dust the pan with flour, then set it aside.

Step 2: Mix the Dry Ingredients

In a medium-sized bowl, whisk together the flour, baking powder, baking soda, and salt. This ensures even distribution of the leavening agents throughout the batter, giving the cake a uniform rise.

Step 3: Cream Butter and Sugar

In a large mixing bowl, beat the butter and sugar together using an electric mixer on medium-high speed until light and fluffy (about 3-5 minutes). The mixture should become pale in color. This process incorporates air, which is essential for the cake’s texture.

Step 4: Add Eggs and Vanilla

Beat in the eggs, one at a time, ensuring each egg is fully incorporated before adding the next. Then, mix in the vanilla extract. Scrape down the sides of the bowl as needed to ensure even mixing.

Step 5: Alternate Adding Dry Ingredients and Milk

Reduce the mixer speed to low. Gradually add the dry ingredient mixture, alternating with the milk and sour cream, beginning and ending with the dry ingredients. Mix just until combined; avoid overmixing as this can result in a dense cake.

Step 6: Bake the Cake

Pour the batter into the prepared baking pan, spreading it evenly with a spatula. Bake for 35-40 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool in the pan for 10 minutes, then transfer it to a wire rack to cool completely.

Step 7: Make the Salted Caramel Sauce

In a medium saucepan, heat the sugar over medium heat, stirring constantly until it melts into a thick, amber-colored liquid. Carefully add the butter, stirring until fully incorporated. Slowly drizzle in the heavy cream, continuing to stir (the mixture will bubble up vigorously). Let the caramel boil for 1-2 minutes, then remove from heat and stir in the sea salt. Allow the sauce to cool slightly before using.

Step 8: Drizzle the Caramel

Once the cake has cooled, use a spoon or a piping bag to drizzle the salted caramel sauce over the top of the cake. Let the caramel set for about 15 minutes before slicing.