In a large saucepan, combine the milk, lemon peel, cinnamon stick, and salt and bring to a simmer over medium-low heat, about 8 minutes.
In a large bowl, beat the egg yolks and sugar with an electric mixer or wire whisk until pale yellow and frothy, about 4 minutes. Add the cornstarch mixture and continue to beat at a low speed until thoroughly mixed. Slowly beat in half of the hot milk mixture, taking 30 to 40 seconds to do so.
Pour the egg-and-milk mixture back into the saucepan and stir continuously over medium heat, making sure the milk does not stick. Stir for 15 to 20 minutes until thickened. Whisk in the vanilla. Remove from the heat.
Remove and discard the cinnamon stick. Pass the custard through a fine-mesh strainer, and then pour into one or individual bowls. Cover with plastic wrap and refrigerate for 4 hours or until ready to serve. Sprinkle with cinnamon. Enjoy!
Note: For an extra hint of sweetness, use orange peel instead of lemon peel. The color of the natilla will be slightly altered but it will be equally delicious.
