Dissolve cornstarch into cold water.
Add in sugar, hot water and salt; blend well and cover with plastic wrap. Microwave for about 5 minutes, stirring halfway through cooking time.
Whisk in the 5 beaten egg yolks and microwave uncovered for 1 1/2 minutes.
Add in the butter and stir until melted.
Blend in lemon juice and zest.
Place filling in pie crust then spread meringue on top, making sure it touches the crust.
Place pie in a 375 degree oven to allow meringue to lightly brown. WATCH!
Remove from oven to cooling rack until about room temperature.
Chill in the refrigerator for a few hours to firm up. Slice with a knife that has been dipped in hot water.