Preheat your oven to 180C (356F) or 160C (320F) for a fan forced oven. Line a cupcake tin with cupcake liners.
In the bowl of a stand mixer fitted with the paddle attachment, add the flour, baking powder, caster sugar and salt. Turn mixer on low speed and allow it to mix for a couple minutes to help everything combine well (alternatively you may do this by sifting the ingredients together). Add the softened butter and let it mix until it resembles a fine sand like texture.
Next, add milk, eggs, yogurt, oil and vanilla extract in a large jug and whisk well.
Add wet ingredients to dry ingredients in a slow and steady stream until no dry ingredients are visible. Scrape down the bowl, add dulce de leche and mix for another 20 seconds.
Fill each cupcake liner 3/4 of the way (using an ice cream scoop to transfer the batter into the cupcake liners makes this a quick and easy process otherwise you can use two tablespoons). Bake for 20-25 min or until a toothpick inserted comes out clean. Allow them to cool completely on a wire cooling rack before frosting.
While your cupcakes are baking, and cooling prepare your buttercream frosting but adding dulce de leche and mix until well combined. Set aside.
To assemble your cupcakes, core the centre using an apple corer or sharp knife and fill with dulce de leche. Fit the end of your piping bag with a 1M tip and frost in a swirl as demonstrated in the video. Finish with a drizzle of salted caramel sauce.