Sour cream lemon pie

1 c. sugar
1/2 c. flour
1/2 t. salt
2 c. milk
1/2 c. sour cream
3 egg yolks
1/4 c. butter
1 1/2 t. lemon zest
1/4 c. lemon juice
1 (9 inch) pie crust
whipped cream

In saucepan, combine sugar, flour and salt.
Gradually stir in milk. Cook and stir on med. heat until thickened and bubbly. Reduce heat, and cook stir for 2 more minutes. Remove from heat.
Beat yolks slightly. gradually stir 1 c. of mix into egg yolks. Return yolk mixture to sauce pan and bring to a gentle boil. Cook and stir for 2 more minutes. Remove from heat and stir in butter, peel and juice. Gently fold in sour cream.
Pour filling into baked pie shell and cool. Top with a dollop of whipped cream if desired.