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1
Preheat oven to 350F.
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2
Butter a 9-inch round cake pan (2 inches deep) and line bottom with a round of wax paper.
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3
Into a bowl sift together flour, baking powder, and salt.
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4
In a large bowl with an electric mixer beat together butter and 1 cup sugar until light and fluffy, about 1 minute.
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5
Separate eggs and beat yolks 1 at a time into butter mixture, beating well after each addition.
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6
In 3 batches alternately beat in flour mixture and milk, beginning and ending with flour mixture.
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7
Add zest and 2 tablespoons lemon juice, beating until just combined (do not overbeat).
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8
In a bowl with cleaned beaters beat whites until they hold soft peaks and beat in remaining 1/4 cup sugar.
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9
Fold whites into batter gently but thoroughly.
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10
Transfer batter to cake pan and bake in middle of oven until a tester comes out clean, 35 to 40 minutes.
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11
Cool cake in pan on a rack and invert onto rack.
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12
Cake may be prepared up to this point 1 day ahead and kept in an airtight container at cool room temperature.
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13
With a long serrated knife horizontally halve cake.
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14
Put bottom half, cut side up, in a 9-inch springform pan.
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15
Brush 2 tablespoons remaining lemon juice over layer.
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16
Working quickly, spread half of blueberry filling evenly over layer, leaving a 1/4-inch border around edge, and top with one third ice cream, spreading evenly.
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17
Put remaining cake half, cut side up, on top of ice cream and brush remaining 2 tablespoons lemon juice over it.
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18
Spread remaining blueberry filling evenly over top, leaving a 1/4-inch border around edge, and spread half of remaining ice cream evenly over filling.
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19
Reserve remaining ice cream for outside of cake.
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20
Freeze cake, covered, until firm, at least 8 hours, and up to 1 day.
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21
Remove side of springform pan.
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22
With a spatula loosen cake from bottom and transfer to a plate.
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23
Frost cake with remaining ice cream, spreading evenly around sides and top of cake.
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24
Freeze cake, loosely covered, at least 2 hours and up to 5 days.
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25
Twenty minutes before serving, garnish top of cake with blueberries and put cake in refrigerator to soften slightly.
