Step 1
Preheat oven to 350 degrees F. Butter and flour two 8-inch cake pans and line bottoms with parchment paper.
Step 2
In a medium bowl whisk together flour baking powder and salt.
Step 3
In a large bowl or the bowl of a stand mixer fitted with the paddle attachment beat butter sugar and stevia until light and fluffy 4 to 5 minutes. Beat in eggs one at a time scraping down bowl and beaters after each addition. Beat in vanilla. Stir in flour mixture until just combined.
Step 4
Divide batter evenly between cake pans. Smooth tops and bake rotating pans halfway through baking until a toothpick inserted in the center comes out clean 30 to 35 minutes. Let cool in pans on a rack for 10 minutes then unmold onto rack to cool completely at least 1 hour.
Step 5
For cranberry sauce combine water sugar stevia in a large saucepan. Bring to a boil and boil 5 minutes. Add cranberries and orange zest and reduce heat to simmer gently until berries are translucent about 5 minutes. Transfer to a bowl to cool completely.
Step 6
For custard whisk sugar stevia egg yolks egg cornstarch and salt together in a medium bowl. Bring milk to a simmer in a medium saucepan. Whisking constantly pour half the milk into the egg mixture. Pour egg mixture whisking constantly back into saucepan with remaining milk. Cook stirring constantly over medium-low until custard thickens about 2 minutes.
Step 7
Scrape custard into a bowl and stir in vanilla. Place a piece of plastic wrap directly on the surface of custard and chill until cold at least 2 hours.
Step 8
For frosted cranberries toss cranberries with egg white to lightly coat. Roll cranberries in sugar then spread out in a single layer on a baking sheet and let dry for 2 hours at room temperature.
Step 9
When ready to assemble trifle make whipped cream. In a large bowl or the bowl of a stand mixer fitted with the whisk attachment beat cream stevia and vanilla on medium speed until stiff. Beat custard in a medium bowl until creamy.
Step 9
To assemble cut cakes into 1-inch chunks. Scatter half the cake cubes in a 2- to 3-quart glass trifle bowl. Spread half the cranberry sauce on top. Top with half the custard. Top with remaining cake cubes then cranberry sauce then custard. Spread whipped cream evenly on top and decorate with frosted cranberries and orange zest.