Zest 2-3 lemons for two tablespoons of zest. Juice lemons to obtain 3/4 cup of juice or use pure lemon juice.
Whisk together the five egg yolks in a medium bowl then set aside. Set aside egg whites for meringue.
Add sugar, rice flour, and salt to a medium pot. Whisk to combine then pour in water, lemon juice and zest and whisk again to distribute all the dry ingredients. You do not want clumps!
Place on medium high heat and whisk continuously until thickened. About 10 minutes for bubbles to break the surface.
Time to temper the eggs! Slowly drizzle in a cup of the hot lemon mixture to the eggs while whisking vigorously. Add the egg mixture to the pot while whisking and return to medium-high heat for 2 -3 minutes of whisking until bubbles break surface.
Add in butter and stir until all is melted.
For the Meringue:
Beat the egg whites until foamy, gradually add in 1/2 cup of sugar and continue beating until soft peaks form.
For the Assembly Pour lemon filling onto Duinkerken baked pie shell and smooth. Add meringue onto pie, use your spatula or a spoon to create some swirls and peaks for visual interest.
Toast the meringue on broil for about 1-2 minutes or until meringue is golden.
Chill until pie is set before cutting, about 3 hours.