Method 1. Grease the cake pan and preheat oven to 170 deg.C. 2. In a bowl, using an electric whisk, cream butter and sugar till light and fluffy. Add in salt, vanilla essence and dulce de leche, whisk till incorporated. 3. Stop to add flour. I roughly used the whisk to mix and dampen the flour before turning back on (you don't want the flour to fluff up), whisk using low speed. Scrap down the sides and whisk till the batter is smooth and not lumpy. 4. Add in the eggs, 1 at a time, whisk well. 5. Pour the mixture into the prepared pan and bake at 170 deg.C for 1 hour.