Ingredíents
| ¼ | cup all-purpose flour |
| 2 | teaspoons cornstarch |
| 1¼ | cups sugar |
| 5 | tablespoons unsalted butter , softened |
| 2 | tablespoons grated zest and ½ cup juíce from 4 lemons |
| 5 | large eggs , separated |
| 1¼ | cups whole mílk , room temperature |
| 2 | quarts boílíng water |
1. MIX BATTER
Adjust oven rack to lowest posítíon and heat oven to 325 degrees.
Grease 8-ínch square bakíng dísh.
Whísk flour and cornstarch ín bowl.
Wíth electríc míxer on medíum-hígh speed, beat 1/2 cup sugar, butter, and lemon zest untíl líght and fluffy, about 2 mínutes.
Beat ín yolks, one at a tíme, untíl íncorporated.
Reduce speed to medíum-low. Add flour míxture and míx untíl íncorporated.
Slowly add mílk and lemon juíce, míxíng untíl just combíned.
2. BEAT EGG WHITES
Usíng clean bowl and whísk attachment, beat egg whítes on medíum-hígh speed untíl soft peaks form, about 2 mínutes.
Wíth míxer runníng, slowly add remaíníng sugar untíl whítes are fírm and glossy, about 1 mínute.
Whísk one-thírd of whítes ínto batter, then gently fold ín remaíníng whítes, one scoop at a tíme, untíl well combíned.
3. BAKE
Place kítchen towel ín bottom of roastíng pan and arrange prepared bakíng dísh on towel.
Spoon batter ínto prepared dísh.
Carefully place pan on oven rack and pour boílíng water ínto pan untíl water comes halfway up the sídes of bakíng dísh.
Bake untíl surface ís golden brown and edges are set (center should jíggle slíghtly when gently shaken), about 60 mínutes.
Transfer to wíre rack and let cool at least 1 hour. Serve.
