2. Sift the flour twice with 1/2 cup of the sugar.
3. With an electric mixer on high speed, beat the egg whites, cream of tartar and salt until soft peaks form when the mixer is removed from the batter. Add half of the remaining sugar and beat for 1 minute. Add the remaining sugar, 2 tablespoons at a time, beating after each addition.
4. Stir in the vanilla. Fold the flour and sugar mixture into the egg whites, 1/4 cup at a time, just until incorporated.
5. Put the batter in an ungreased 10" tube pan and bake until the cake is a light golden brown and springy to the touch, about 1 hour. Invert the pan and let the cake cool completely before removing from the pan. This can be done in advance and stored in an airtight container for 1-2 days.
6. To make the custard: Whisk the eggs, sugar and cornstarch together in a saucepan. In another saucepan, bring the milk and vanilla to a boil. Remove from heat and slowly whisk the hot milk into the eggs.
7. Cook the custard over medium heat, while whisking constantly until the mixture comes to a boil. Remove from heat. This can be made in advance and stored in the refrigerator for up to 2 days. Stir in 1 1/2 pints of berries.
8. To make the rum syrup: Bring the sugar and water to a boil in a small saucepan. Remove from heat and add the rum.
9. To assemble the trifle: Line the bottom of a trifle dish or large glass bowl with slices of angel cake. Brush some of the syrup over the cake and let it soak in. Mix the preserves and orange juice together and spoon 1/3 of this mixture over the cake slices. Spoon 1/2 of the custard over the preserves. Repeat with cake, syrup, preserves, custard, cake, syrup and preserves. This can be stored in the refrigerator for up to 24 hours.
10. Finish the trifle by spreading the whipped cream over the top and decorating it with the remaining berries.