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1
Preheat the oven to 325F.
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2
Lightly oil the bottom only of a 10-inch tube pan with canola oil spray.
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3
In a large bowl, sift in the flour, then stir in the vanilla extract, lemon extract, and lemon zest.
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4
In a separate bowl, with an electric mixer beat the egg whites on medium speed until frothy.
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5
Add the cream of tartar and beat until soft peaks form, about 1 to 2 minutes.
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6
Gradually add the agave nectar and increase to high speed.
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7
Beat until stiff and glossy, but not dry, about 1 minute.
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8
Gently fold the egg whites into the flour mixture.
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9
Spoon the batter into the prepared pan.
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10
Using a serrated knife, cut though the batter to remove any air bubbles.
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11
Bake for 45 minutes, or until a toothpick inserted into the center of the cake comes out clean.
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12
Remove from the oven and invert on a cooling rack to cool completely.
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13
To prepare the frosting, in a saucepan bring the agave nectar to a boil over medium heat.
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14
Let simmer for 3 to 4 minutes, stirring occasionally, then set aside.
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15
In the top of a double boiler, over medium heat, beat the egg whites, cream of tartar, and lemon juice with an electric mixer, or by hand with a balloon whisk, for 4 to 5 minutes, until light and foamy.
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16
Slowly drizzle the hot agave nectar into the egg whites, beating constantly for another 4 to 5 minutes, until the frosting is thick.
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17
Beat in the lemon extract and vanilla extract and beat 2 minutes more.
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18
The frosting should be smooth, fluffy, and of spreading consistency.
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19
When the cake has cooled completely, slice it in half horizontally using a serrated knife.
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20
Fill the cake with half the frosting and some blueberries.
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21
Top with the other cake half.
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22
Spread the remaining frosting on top and garnish with the remaining blueberries.
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23
Serve soon after frosting to maintain this cakes light, airy texture.
