Preheat the oven to 350 degrees F (175 degrees C). Grease an 8x8-inch baking pan thoroughly.
Blend butter and sugar with an electric mixer until combined and creamy. Add egg and vanilla extract; beat until incorporated. Scrape down the sides of the bowl and beat again. Combine flour and salt. Add to the butter mixture and mix until a ball of dough forms.
Press 2/3 of the dough into the bottom of the baking pan.
Bake in the preheated oven until set and light brown, about 20 minutes.
Pour dulce de leche over the crust, trying to keep the edges mostly bare.
Add coconut and pecans to the remaining dough and mix until incorporated. Crumble mixture over the dulce de leche, pressing it lightly over the top.
Bake until lightly browned, about 15 minutes. Let cool completely before cutting into bars.
