Preheat oven to 170 C / Gas 3. Butter a 20x30cm baking tin.
In a large glass or metal bowl, beat egg whites with cream of tartar and vanilla until soft peaks form. Gradually add sugar while continuing to beat to stiff peaks. Fold in cracker crumbs and pecans until evenly blended. Spread evenly in the prepared tin.
Bake for 30 minutes in the preheated oven, until the cake springs back when pressed in the centre. Let cool.
Meanwhile, make the topping. Mix together the pineapple and whipped cream. Spread over cooled cake and refrigerate until serving.