Place egg whites in a large bowl; let stand at room temperature for 30 minutes. Add the water, vinegar, vanilla, baking powder and salt. Beat on medium speed until soft peaks form. Gradually beat in sugar, 2 tablespoons at a time, on high until stiff glossy peaks form and sugar is dissolved.
Spread evenly into a greased 13x9-in. baking pan. Bake at 300° for 45 minutes. Turn off oven and do not open door; let crust dry in oven overnight.
For filling, in a bowl, dissolve gelatin in boiling water. Stir in the strawberries, lemon juice and salt (mixture will thicken quickly). Fold in cream. Spread over crust. Store in the refrigerator.