Dulce de Leche Tartlets

Preheat oven to 350 degrees F and lightly grease mini muffin pan. Form 1 tablespoon balls of sugar cookie dough and roll in little sugar to prevent sticking. Fill each muffin hole with 1 tablespoon ball, pressing down and up the sides. Bake tarts until lightly golden, 10 to 12 minutes. Use end of wooden spoon to press down on the center to make room for the filling. Allow tarts to cool in pan for 5 minutes, then gently transfer to cooling rack to let cool completely. Fill tartlets with dulce de leche and sprinkle with flaky sea salt.