First make the syrup. Bring the sugar and water to a boil over medium high heat. Reduce heat to low and allow to boil until the sugar dissolves completely, about 5 to 7 minutes. Remove from heat, stir in the lemon juice, and set aside to cool.
Now you can start making the custard. Preheat the oven to 350 degrees Fahrenheit. Warm the milk in a medium-sized pot over medium heat. Whisk in the sugar and salt until combined. Add the semolina slowly, shaking it over the pot while whisking constantly to prevent clumps from forming. Continue to warm the mixture, whisking constantly, until it is hot but not boiling. Then lower the heat.
Place the whisked egg yolks in a medium-sized heat safe bowl. Slowly ladle some of the milk mixture into the egg yolks, whisking all the while. Continue adding the milk to the egg yolks in this gradual manner until half of the milk mixture has been blended into the egg yolk mixture.
Pour the egg yolk mixture back into the pot of the milk mixture and whisk well. Allow the custard to continue cooking and thicken for 3 minutes over low heat, whisking constantly. Remove from heat, and whisk in the nutmeg, vanilla extract, and grated lemon zest. Stir in 3/4 cup of the blueberries.
Remove from the oven and gently pierce the surface of the custards in 4 or 5 places with a fork. Arrange the remaining 1/4 cup blueberries on top of the custards in a centered circle, then pour 2 tablespoons of the syrup over each ramekin. Allow them to rest and absorb the syrup for 30 minutes. Serve immediately, and keep any leftovers refrigerated.