Lemon Angel Pie

Preheat oven to 275°. Generously butter a 9-in. pie pan, preferably glass, and set aside. In bowl of a stand mixer, whip egg whites on high speed until frothy. Sprinkle with cream of tartar and whip until whites hold a soft peak when whisk is lifted. Gradually rain in 1 cup of the sugar (2 tbsp. every 20 seconds), until whites are glossy; hold a stiff, straight peak when whisk is lifted; and no longer feel grainy between fingers, 5 to 6 minutes total.

Scrape meringue into pan. With back of a soup spoon, create a tall pie shell: Spread meringue fairly flat on pan bottom and then swirl it 1 to 1 1/2 in. above and just inside rim rather than on it, since meringue will expand over rim as it bakes. Bake just until surface of meringue feels crisp and dry in center and is barely starting to color, 40 to 45 minutes. Crust will be fragile and layer underneath will be soft and moist. Let cool on a wire rack.

In a medium metal bowl, whisk egg yolks, the remaining 1/2 cup sugar, zest of 3 lemons, and lemon juice until blended. Set over a pan filled with 1 in. simmering water and cook, whisking constantly, until curd thickly coats a metal spoon and reaches about 180° on an instant-read thermometer (tip bowl to check), 8 to 11 minutes. Set bowl in a larger bowl of ice and water and let cool, whisking often; chill until used.

Whip cream until thick. Stir a spoonful into lemon curd, then fold in the rest. Spoon mixture into meringue shell, swirling top. Chill at least 2 hours to mellow. Scatter long lemon zest strands on top if you like.

MAKE AHEAD Chilled airtight up to 1 day.