1 c. all-purpose flour
1/4 c. brown sugar
1/4 c. ground nuts
1/4 c. (1/2 stick) cold butter, cut into bits

FILLING:

2 lb. or 2 (15 oz.) containers light or part skim ricotta
3 egg whites
2 eggs
1 c. buttermilk
1/2 c. sugar
1/4 tsp. salt, optional
2 tsp. vanilla extract
Grated rind of 1 lime or grated rind of 1/2 lemon
2 tbsp. fresh lime juice or lemon juice