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1
Preheat oven to 350 degrees.
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2
Grease three 9-inch cake pans and line with parchment or waxed paper.
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3
Mix flour, baking powder and salt and sift onto a piece of waxed paper or parchment.
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4
In a large mixing bowl, beat sugar and butter until light and fluffy, scraping sides as needed.
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5
Whisk egg whites until well blended but not foamy, and add to batter in 4 batches, making sure each addition is well incorporated.
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6
Add dry ingredients and milk to batter, alternately, in 4 batches, mixing each only until just blended.
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7
Mix in vanilla.
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8
Divide batter among 3 pans.
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9
Gently drop each one on a counter to eliminate large air bubbles.
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10
Bake for about 20 minutes or until cake springs back in center when pressed or a cake tester comes out clean.
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11
Let rest for 5 minutes, then remove cake from pan and cool completely on rack.
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12
Meanwhile, make curd: Put all ingredients in a non-reactive saucepan and whisk to blend.
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13
Set over medium heat and cook, stirring constantly, until filling thickens and a candy thermometer registers 170 degrees.
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14
This can take 10 to 15 minutes.
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15
Do not let filling simmer or boil.
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16
Remove from heat and pour into a bowl to cool to room temperature.
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17
Place a cake layer on a cake stand or plate and spread 2/3 cup curd on top to the edges.
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18
Stack another layer and continue until all layers have been used.
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19
Use remaining curd on top and sides.
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20
Filling is somewhat translucent, so layers will be visible through curd on sides.
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21
If layers slide while frosting, push 3 or 4 long wooden skewers through them to hold until cake sets.
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22
Cake is best left covered at room temperature overnight.
