Preheat the oven to 350°F (175°C) and grease two 9-inch round cake pans. If you like, line the pans with parchment paper and grease the paper as well.
Whisk together the flour, baking powder, baking soda, and salt. Set aside.
Using an electric mixer on medium speed, beat the butter and sugar together until light and fluffy. Add the eggs one at a time, beating well after each addition.
Mix in the dulce de leche and vanilla extract until fully combined.
With the mixer on low speed, gradually add the dry ingredients in three portions, alternating with two portions of the buttermilk. Mix until just combined.
Divide the batter evenly between the pans and bake for 35-40 minutes or until a toothpick comes out clean.
Cool the cakes in the pans on a wire rack for 10-15 minutes before removing them from the pans to finish cooling on a wire rack.
To make the frosting:
Using an electric mixer on medium speed, beat the butter until smooth and creamy.
Mix in the dulce de leche and vanilla extract until well combined.
Gradually beat in the confectioners' sugar, mixing well. Add heavy cream as needed to achieve your desired frosting consistency.
Once the cakes are completely cool, place one layer on a cake plate and frost the top. Place the other layer on top, and frost the top and sides. If you like, garnish with toasted nuts.
Notes
Store in an airtight container at cool room temperature for up to 2 days or in the refrigerator up to 5 days.
For tips, step-by-step photos, and extra details, be sure to read the full post above before starting. It’s packed with helpful info to answer common questions!