Preheat the oven to 350°F / 175°C. Butter a 7" cake pan and coat it with granulated sugar.
To a medium sized mixing bowl, add the flour, baking powder, salt, sugar, and cubed butter. Use a hand mixer or a stand mixer fitted with the paddle attachment to beat the mixture together until the butter has completely combined with the dry ingredients and no lumps remain.
Add in the oil, egg, dulce de leche, vanilla, sour cream, and milk. Whisk the ingredients together just until a cohesive batter has formed.
Pour the cake batter into your prepared pan, then bake for 30-35 minutes, until a toothpick inserted into the center of the cake comes out with just a few moist crumbs.
Allow the cake to fully cool to room temperature before assembling.
Dulce de Leche Milk Soak
Add the dulce de leche and milk to a microwave safe measuring cup. Microwave for 30 seconds, then stir the mixture and microwave it for another 30 seconds. Your dulce de leche should be melted and combined with the milk, but if it's not, microwave in 10 second intervals until it is.
Poke a bunch of small holes in to the top of your room temperature cake in the springform pan. Pour the milk soak over the cake and leave it to sit while you make the whipped cream.
Dulce de Leche Whipped Cream
In the bowl of a stand mixer fitted with the whisk attachment, or with a hand mixer, beat together the heavy whipping cream, dulce de leche, vanilla, and salt until soft peaks form.
Assembling the cake
Wash and cut the strawberries in half, leaving some whole for the looks if desired (like in the pictures.)
Gently dollop the 200g of dulce de leche on top of the cake, and spread around into an even layer.
Pile on the whipped cream and gently spread it around, then pile on the strawberries.