Preheat your oven to 325°F (163°C). Generously grease and flour three 8-inch round cake pans or spray them with non-stick baking spray to ensure easy release.

In a stand mixer fitted with the paddle attachment (or using a hand mixer), beat the butter and vegetable oil together on high speed for 2 minutes until smooth and creamy. Gradually add the granulated sugar and continue beating on high speed for 4–5 minutes, until the mixture becomes very pale yellow, light, and fluffy.

Add the eggs one at a time, mixing well after each addition. Scrape down the sides and bottom of the bowl as needed to ensure everything is fully incorporated. Mix in the vanilla extract.

In a separate bowl, sift together the cake flour, baking powder, salt, and baking soda. With the mixer on the lowest speed, slowly add the dry ingredients to the wet ingredients in two additions. Be careful not to overmix—just mix until the flour is incorporated.

Finally, add the sour cream and heavy whipping cream, mixing just until the batter is smooth and fully combined. Scrape down the bowl one last time and give the batter a gentle final mix by hand if needed.

Divide the batter evenly between the prepared cake pans. Bake for 17 to 24 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Do not overbake. Begin checking for doneness around 16 minutes, as oven temperatures can vary.

Remove the cakes from the oven and let them rest in the pans for 10–15 minutes. Carefully invert them onto wire racks and allow them to cool completely before assembling.

In a large, heavy-bottomed saucepan, combine the butter, evaporated milk, and sugar. Cook over medium-low heat, stirring constantly, until the butter is melted and everything is well combined.

Continue to cook over medium-low heat for 1½ to 2 hours, stirring regularly, until the mixture thickens and develops a deep golden-brown color. This step requires patience—watch closely to prevent burning. You can slightly increase the heat to speed up the process, but stir constantly and carefully to avoid scorching.

The caramel is ready when it thickly coats the back of a spoon and has a smooth, rich texture. Once the desired consistency and color are achieved, remove from heat and stir in the vanilla extract.

Let the caramel cool for 15–20 minutes to thicken further before using it to frost the cake. If it remains too warm and runny, you can place it in the refrigerator briefly to help it firm up.

Optional Tip: For a lighter, whipped frosting texture, you can transfer the cooled caramel into a stand mixer and whip it on medium speed until fluffy.

Ensure the cake layers are completely cool before assembly.

Place a small spoonful of icing in the center of your cake plate or stand to help anchor the cake. Set the first cake layer on top and spread about ¼ of the caramel icing evenly over the surface using an offset spatula. Allow it to set for 5 minutes.

Place the second layer directly on top, aligning it carefully. Spread another ¼ of the caramel icing over it and let it sit another 5 minutes.

Add the final cake layer, then spread the remaining icing generously over the top and around the sides of the cake. Smooth the edges with a spatula or leave it rustic, depending on your preference.

Let the assembled cake sit for about 30 minutes at room temperature to allow the icing to set. Slice and serve—prepare for rave reviews!