For the blueberry lemon curd: In a medium pot, stir the blueberries, lemon juice, granulated sugar and salt to combine, then cook over medium heat, stirring frequently, until the berries break down and the mixture becomes juicy, 5 to 7 minutes. While the mixture heats, whisk together the eggs and egg yolks in a medium bowl.
When the blueberries are soft and broken down, strain the mixture into the bowl with the eggs, pressing firmly on the solids inside the strainer to release all of the liquid (discard the solids). Whisk the hot liquid well to combine with the eggs, then return it to the pot.
Place the pot over medium-low heat and cook, whisking constantly, until the mixture begins to thicken, 3 to 5 minutes. Once it starts to thicken, switch to a silicone spatula to help ensure you get into the corners of the pot. Whisk or stir in the butter 1 piece at a time, stirring well after each addition. Remove from the heat.
Strain the curd into a medium bowl, cover directly with plastic wrap and transfer to the fridge to cool completely (or speed up the process by straining onto a baking sheet and covering directly with plastic wrap).
For the strawberry sauce: In a medium pot, toss the strawberries and lemon juice together to combine. Cook over medium heat until the mixture starts to become juicy, 1 to 2 minutes. In a medium bowl, whisk the granulated sugar, cornstarch and salt together to combine.
Sprinkle the sugar mixture over the fruit in the pot and stir well to combine. Continue to stir over medium-low heat until the mixture thickens, 1 to 2 minutes. Transfer to a bowl or storage container and store in the refrigerator to cool completely.
To assemble the trifle: Place the cream in the bowl of an electric mixer fitted with the whip attachment. Add the powdered sugar and vanilla and whip to stiff peaks.
To assemble, start with a layer of whipped cream (using about 1/5 of the cream) in the base of a 9-inch trifle dish, then scatter a layer of angel food cake on top (using about 1/4 of the cake). Top the cake with about half of the blueberry lemon curd, using the back of a spoon to help nudge it into an even layer.
Repeat this step, but this time replace the curd with half of the strawberry mixture.
Repeat the steps with the whipped cream, blueberry and strawberry layers, continuing to build up layers in the trifle, finishing with a layer of whipped cream. Refrigerate until ready to serve (up to 8 hours).