In a saucepan, melt the butter. Remove from the heat; add flour and stir until smooth. Stir in brown sugar. Return to heat; stir in milk and salt until blended. Cook and stir over medium-high heat until thickened and bubbly. Reduce heat; cook and stir 2 minutes longer. Remove from the heat. Stir about 1 cup hot filling into the egg yolks; return all to pan, stirring constantly. Bring to a gentle boil; cook and stir for 2 minutes longer. Remove from the heat. Gently stir in vanilla. Pour into pastry shell.

For meringue, beat egg whites and cream of tartar in a small bowl on medium speed until soft peaks form. Gradually beat in sugar, about 1 tablespoon at a time, on high until stiff glossy peaks form and sugar is dissolved. Spread evenly over hot filling, sealing edges to crust.

Bake at 350° for 12-15 minutes or until meringue is golden brown. Cool on a wire rack for 1 hour. Refrigerate for at least 3 hours before serving. Refrigerate leftovers. Yield: 6-8 servings.