Preheat the oven to 350ºF, and spray a 9x13-inch baking dish with nonstick cooking spray.
In a large mixing bowl, stir all of the cake ingredients together until smooth; batter will be thick.
Pour batter into prepared baking dish. Bake for 28-32 minutes, or until toothpick inserted in the center comes out clean. Allow cake to cool completely, then cut into cubes.
Make the Sauce:
in a medium saucepan, heat the blueberries over medium heat until they soften and their juices start to release, about 2-3 minutes. In a separate bowl, combine the sugar, cornstarch, and salt. Add mixture to the blueberries and continue cooking until a sauce forms and it begins to thicken, about 4-6 minutes. Remove from heat and stir in the lemon juice. Pour into a shallow bowl and place in the refrigerator to cool completely.
Make the Filling:
In the well-chilled bowl of a stand mixer fitted with a whisk attachment, beat the heavy cream until stiff peaks form. Transfer whipped cream to another bowl and place in refrigerator to keep chilled.
Return bowl to mixer, and switch whisk attachment out for paddle attachment. Beat the cream cheese until smooth. Add powdered sugar, lemon juice, zest, vanilla, almond extract, and salt; continue beating until smooth and incorporated.
Add a quarter of the whipped cream and beat until combined. Remove bowl from mixer and use a spatula to fold in the rest of the whipped cream.
To Assemble:
Place half of the cake cubes into the bottom of a large trifle dish or bowl. Spoon half of the lemon filling on top, spreading evenly. Pour half of the blueberry sauce evenly over the filling. Sprinkle 1/2 cup of fresh blueberries on top. Layer the rest of the cake on top of the blueberries. Spread the rest of the lemon filling on top. Pour the remaining blueberry sauce evenly over the filling.
Pipe a border of whipped cream along the top of the trifle*. Decorate with the rest of the blueberries along with fresh-cut slices of lemon. Refrigerate for at least 2 hours before serving.
Notes
*To make the whipped cream, I just whipped up 1 cup of heavy cream until soft peaks formed. Then I added 1/3 cup powdered sugar, 1/2 teaspoon vanilla, and 1/8 teaspoon of almond extract, and continued whipping until stiff peaks formed.