Mix the oil, sugar, and eggs in a large bowl.

Sift the flour with the baking powder in another bowl.

Combine the milk and vanilla extract in a separate container.

Using a mixer or whisk, gradually add the flour mixture and the milk mixture to the oil, sugar, and eggs. See tip.

With a spoon or piping bag, fill each liner about 1/2 inch high with batter, then add a teaspoon of dulce de leche in the center. Fill with more batter until each liner is about 2/3 full.

Bake at 350°F (175°C) for 18 minutes.