Combine the milk, half & half, and orange zest in a medium sauce pan. Affix a candy thermometer to the side of the pan, then place it over medium-high heat and cook, stirring occasionally, until the mixture reaches 180◦.
Remove the pan from the heat, cover, and let stand for 10 minutes.
Meanwhile, combine the sugar, salt, and egg yolk in a medium bowl and whisk until it becomes pale.
Gradually add a little of the milk mixture to the egg mixture while whisking vigorously. Continue adding and whisking until the two mixtures are fully combined, then return it all to the pan.
Place the pan over medium-low heat and cook until the mixture reaches 160◦, whisking constantly.
Transfer the mixture to another bowl and add the vanilla extract. After it cools to room temperature, place the bowl in the refrigerator overnight.
Remove the bowl from the refrigerator and add the pineapple. Follow your ice cream maker's instructions for freezing. Transfer the ice cream to a freezer-safe container for a few hours to firm it up a little more if you would like.