For the meringue layers, pulse the almonds in the food processor until coarsely ground; place them on a baking pan and toast for about 15 minutes, stirring frequently, until golden.
Cool and combine with the sugar and cornstarch; reduce oven to 300.
Whip the egg whites on medium speed with the salt until white and opaque; increase speed to maximum and whip in remaining sugar - Continue whipping until egg whites hold a firm peak.
Fold in extracts and toasted almond mixture.
Pipe batter on paper-lined pans with a pastry bag fitted with a 1/2-inch plain tube to make three 10-inch disks.
Bake at 300 about 30 minutes, until crisp but not completely dry; cool layers on pans.
FOR THE FILLING - Place the sugar and lemon juice in a saucepan and stir well to combine; place on medium heat and stir occasionally until the sugar melts and caramelizes.
Add the milk carefully (the caramel will splatter) and return to a boil, stirring to dissolve any hardened caramel.
Whisk yolks in a bowl with orange zest and whisk half the boiling milk into them; return remaining milk to a boil and whisk in yolk mixture, continuing to whisk until thickened.
Strain into a bowl and cool.
Beat butter with paddle on medium speed until soft and light; beat in custard cream and beat filling smooth.
FOR THE GLAZED ORANGES - Combine the orange juice and gelatin in a bowl.
Bring the apricot preserves to a boil over low heat, stirring occasionally; add the orange mixture and return to a boil, reducing slightly. Strain and cool slightly.
Halve and slice oranges thinly; dip orange slices in glaze and place on a pan lined with plastic wrap to set.
To assemble, trim layers to an even 10-inch diameter and place one on a cardboard; spread with 1/4 of the filling.
Repeat with another layer and another 1/4 of the filling; top with last layer and mask cake with another 1/4 of the filling.
Use the remaining filling to make a border of rosettes on the edge of the cake and a circle of rosettes in the center; press the sliced almonds against the side of the cake and fill in the center circle with them.