My grandma makes the best lemon meringue pie I've ever had, and it's similar in a lot of ways. Except instead of water and cornstarch to give the filling body, she uses a can of condensed milk.
So you add the yolks directly into the condensed milk at room temp.Then add sugar, lemon juice, and zest in and mix well. Toss it in the oven for a few minutes to give the meringue some color. Then let it cool.