This sounds similar to what you described:
RITZ CRACKER DESSERT
40 Ritz crackers
1 stick butter, melted
4 egg whites
1/2 tsp. vinegar
1/4 tsp. cream of tartar
1 c. sugar
1 can lemon pie filling or sm. Jello lemon pie filling (cooked)
1 (9 oz.) Cool Whip
Crush crackers and combine with melted butter. Spread in 9 x 13 inch dish (or pan). Beat egg whites with vinegar. When stiff add cream of tartar, then sugar gradually. Spread over the cracker crust and bake at 350 degrees for 18 minutes or until golden brown. Cool. Then spread on lemon pie filling. Top with Cool Whip.