01 - Toss sliced strawberries with sugar and lemon juice in a medium bowl. Set aside for 15-20 minutes until juicy.
02 - Heat milk in a saucepan over medium heat until steaming. Whisk egg yolks, sugar, cornstarch, and salt until pale and smooth. Gradually pour hot milk into egg mixture while whisking constantly. Return mixture to saucepan and cook over medium heat, stirring constantly, until thickened and bubbling, about 3-5 minutes. Remove from heat and stir in vanilla extract. Cover surface with plastic wrap and chill until cooled.
03 - Beat heavy cream, powdered sugar, and vanilla extract in a chilled bowl until soft peaks form. Refrigerate until ready to use.
04 - Layer half of the cake cubes in a large trifle bowl or glass dish. Spoon half of the macerated strawberries with juices over the cake. Spread half of the cooled custard over the strawberries. Repeat layers with remaining cake, strawberries, and custard. Top with whipped cream, spreading evenly or piping decoratively.
05 - Refrigerate assembled trifle for at least 30 minutes before serving to allow flavors to meld.