Lemon Sponge Pie

1cup sugar, 4T butter, 3 eggs (separated), 3T flour, 1/4t salt, 1 1/4c whole milk, 4T lemon juice (1 lemon). Cream butter and sugar, mix in egg yolks, flour and salt. Mix in milk and lemon juice until frothy. Fold in well beaten(stiff) egg whites until just mixed. Pour in 9" crust and bake at 400 for 10 minutes. Reduce heat to 375 and bake additional 25-30 minutes until done.