Preheat your oven to 350°F (175°C) to ensure even baking.
Grease a 9x13-inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, beat together the softened butter and brown sugar until light and fluffy, about 2-3 minutes.
Add the eggs and vanilla extract to the mixture, and beat until fully combined.
In another bowl, whisk together the flour, baking powder, and a pinch of salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined.
Spread half of the cookie dough mixture into the prepared baking pan. Drizzle half of the dulce de leche over this layer. Sprinkle the halved Rolo candies on top, followed by the remaining dulce de leche.
Dollop the remaining cookie dough mixture over the top, leaving some gaps for the filling to peek through.
Bake for about 25-30 minutes, or until the edges are golden brown and a toothpick comes out with a few moist crumbs.
Let the pan cool for 10-15 minutes, then transfer to a cooling rack to cool completely before cutting into squares.