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1
Preheat the oven to 350F.
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2
Stir together flour and 3/4 cup brown sugar.
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3
Sift twice.
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4
Put egg whites into the bowl of an electric mixer fitted with the whisk attachment.
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5
Beat on medium speed until foamy.
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6
Add cream of tartar and salt.
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7
Raise speed to high, and beat until soft peaks form.
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8
Sprinkle half the remaining 3/4 cup brown sugar over egg white mixture, and beat until combined.
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9
Sprinkle the remaining brown sugar over egg white mixture, and beat until stiff, glossy peaks form.
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10
Transfer egg white mixture to a large bowl.
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11
Fold in flour mixture in 3 batches, folding in lemon zest with last batch.
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12
Spoon batter into an ungreased 10-inch tube pan (not nonstick) with a removable bottom.
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13
Run a knife through batter to eliminate air pockets.
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14
Bake until cake is golden and springs back when lightly touched, about 45 minutes.
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15
Invert pan onto its legs or over a narrow-neck bottle; let cool 1 hour.
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16
Reinvert, and run a knife around sides and tube to loosen; remove sides.
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17
Run a long knife along bottom of cake; remove from tube.
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18
Place cake on a serving platter.
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19
Cut a slit in rind of candied citrus slices; twist slices, and arrange around bottom of cake.
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20
Reserve 1 slice for hole in center.
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21
Put creme fraiche into a medium bowl.
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22
Whisk until lightened.
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23
Transfer a little more than 1/4 cup to a pastry bag fitted with a large rose tip (such as Ateco #123).
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24
Decoratively pipe creme fraiche around top edge of cake.
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25
Place 1 citrus slice over hole; pipe creme fraiche around it.
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26
Serve remaining creme fraiche on the side.
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27
Cut a round of parchment paper to fit just inside a medium pot; set aside.
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28
Bring sugar and 3 cups water to a simmer in pot, stirring until sugar has dissolved.
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29
When liquid is clear and bubbling, reduce heat to medium-low.
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30
Add citrus slices, arranging them in a slightly overlapping layer.
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31
Cover with the parchment paper round.
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32
Place a cake pan on top of parchment to keep slices submerged.
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33
Simmer (do not boil) until rinds are almost translucent, about 40 minutes.
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34
Let cool completely in syrup.
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35
The candied citrus slices can be stored in syrup up to 1 week.
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36
Line a baking sheet with parchment paper; set a wire rack over sheet.
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37
Transfer candied citrus to rack.
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38
Let stand until dry and slightly firm, about 8 hours.
