Pre-heat the oven to 350 degrees F (177 degrees C).
In a large pan, combine 1 cup of sugar, cornstarch and salt. Mix pineapple juice and sugar until well combined. Bring to a rolling boil, then cook and stir for about 2 minutes until the mixture thickens. Remove from heat.
Pour 1 cup of the hot filling into a bowl with egg yolks. Stirring constantly, add the filling to the pan. Bring mixture to a gentle simmer; cook for 2 minutes, stirring constantly. Remove from heat. Add lemon juice to warm.
In a large bowl, beat the egg whites with cream of tartar to make meringue until soft peaks appear. Beat remaining 6 tablespoons of sugar slowly, 1 tablespoon at time, with high speed until stiff peaks are formed.
Filling should be poured into the shell. Spread meringue on top of the filling and seal edges.
Bake the meringue in a preheated, hot oven for 15 minutes or until it is golden brown. After cooling on a rack, refrigerate the meringue for 3 hours.