Filling: Mix 1 ½ cup sugar, cornstarch and water in a saucepan over medium heat, stirring constantly, until mixture thickens and boils. Remove from heat, whisk in egg yolks one at a time, stirring constantly. Add lemon juice, lemon zest and 2 drops of food coloring. Pour filling into pie crust.
Meringue: In a mixing bowl, beat egg whites and cream of tarter until foamy. Beat in 6 tablespoons of sugar, one tablespoon at a time, continue beating until stiff and glossy. Beat in vanilla. Spread meringue over hot pie filling, carefully sealing to edge of pie crust.
Bake for 10 minutes or until it starts to brown a little. Cool completely, then refrigerate until ready to serve.