Puree the mango in a food processor until as smooth as possible.
In a medium bowl, whisk together the mango, egg yolks, orange zest, orange juice, sugar, and salt. Transfer to a medium saucepan.
Cook the mixture over low-medium heat until it is thick enough to coat the back of a spoon, 5 to 7 minutes.
Remove from heat and add the butter. Mix until smooth.
Transfer the curd to a small bowl and cover with plastic wrap.
Refrigerate until chilled, about 30 minutes.