Preheat your oven to 350°F (175°C) and prepare a cupcake pan with liners.
In a bowl, whisk together the flour, baking powder, baking soda, and salt.
In a separate bowl, cream the softened butter and sugar until light and fluffy.
Add the eggs, one at a time, beating well after each addition, and mix in the vanilla extract.
Mix in the dry ingredients alternately with the buttermilk, starting and ending with the flour mixture.
Fold in the dulce de leche until just combined, avoiding overmixing.
Spoon the batter into the prepared cupcake liners, filling them about two-thirds full.
Bake for 20-22 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cupcakes to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
Prepare the frosting by beating additional dulce de leche with butter until creamy, then frost the cooled cupcakes.
