Prepare the Mixture
In a saucepan, combine the milk, sugar, and salt. Place over medium heat and stir until the sugar dissolves.
Gradually whisk in the semolina flour, ensuring there are no lumps.
Cook the Mixture
Continue to cook the mixture, stirring constantly with a whisk or wooden spoon until it thickens. This should take about 10-15 minutes.
Once thickened, remove from heat and stir in the butter (or coconut oil) and vanilla extract (or lemon zest) until smooth.
Transfer to Molds
Pour the semolina mixture into serving cups or molds. Smooth the top with a spatula for an even surface.
Allow the budino to cool slightly at room temperature.
Chill
Cover the cups or molds with plastic wrap and refrigerate for at least 2 hours, or overnight for the best texture.