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1
Preheat oven to 350F and butter an 8- by 2-inch square metal baking pan.
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2
Line bottom of pan with parchment or wax paper, then butter paper.
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3
Dust with flour, knocking out excess.
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4
Whisk together yolks, 1/2 cup sugar, milk, and vanilla in a large bowl until combined well.
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5
Whisk in flour and salt (batter will be thick).
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6
Beat whites with an electric mixer until they hold soft peaks.
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7
Gradually beat in remaining 1/4 cup sugar and beat until whites hold stiff, glossy peaks.
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8
Stir about one third of whites into batter to lighten, then fold in remaining whites in 2 more batches, gently but thoroughly.
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9
Transfer batter to baking pan, spreading evenly, and bake in middle of oven until pale golden and a tester comes out clean, 14 to 16 minutes.
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10
Cool cake completely in pan on a rack (cake will shrink from sides of pan).
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11
When cool, run a sharp knife around side of cake if necessary and invert onto rack, then remove paper.
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12
Scrape seeds from vanilla bean with tip of sharp knife into a small saucepan, then add pod.
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13
Add sugar, water, zest, and juice.
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14
Bring to a boil, stirring until sugar is dissolved, and boil 1 minute.
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15
Transfer to a bowl and chill 30 minutes.
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16
Pour syrup through a fine sieve into another bowl and discard solids.
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17
Gently stir in strawberries and let stand 15 minutes.
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18
Beat together cream, sugar, and sour cream until mixture just holds stiff peaks.
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19
Cut 4 rounds from cake with cookie cutter.
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20
Generously brush both sides of each round with syrup from strawberry mixture and arrange, darker sides up, on plates.
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21
Spoon strawberries onto rounds and let stand 5 minutes to allow more syrup to soak into cake.
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22
Top rounds with dollops of cream and drizzle with remaining syrup.
