I prefer to top with meringue. For a perfect key lime meringue use the 5 egg whites that were left over for the pie filling. Place in bowl and whip until peaks just start to form. Then add a scant amount of salt (about 1/4 tsp) and whip again for 30 seconds. Add in 9 tablespoons of sugar; adding 1 tablespoon at a time and whipping for about 30 seconds between each tablespoon. Last add 1/4 teaspoon lime juice and continue whipping until peaks are formed. Pile on top of pie and bake in 300 degree oven for about 10 minutes or until it is golden and the peaks are browned.