In the bowl of a stand mixer (or a large bowl with hand mixer) fitted with the whisk attachment, combine together the egg whites, sugar and vanilla
Whip on low speed, about 1 minute.
Increase the speed to medium low and whip for 3-4 more minutes. The egg whites should look really dense.
Add the lemon juice followed by the salt.
Mix on medium for 3 more minutes.
Increase the speed yet again to high and whip for 3 minutes.
After the last three minutes the egg whites should be at “soft peaks” : the egg whites runs slowly of the whisk, but still retains some body.
Remove the bowl from the stand mixer. Sprinkle in the flour evenly over the mixer. Stir gently with a flexible spatula to dissolve the flour and then switch to a folding method. Fold the eggs whites and flour together until the no flour remains.
Pour the batter into a 10 inch tube pan.
Bake for 45-48 minutes, until the cake has a golden crust and has risen to the rim of the pan.
Cool inverted immediately. If your cake pan has stilts, use them, otherwise get creative. Cool upside down for 2 hours until no warmth remains.
After the two hours is up, turn the cake right side up and loosen the cake from the pan. Invert onto a serving plate. Cut with a serrated knife.
Serve topped with fresh berries and whipped cream.
The angel food cake wrapped in plastic wrap can last for 1 week at room temperature.