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1
Position rack in center of oven; preheat to 350F
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2
Coat a 10-inch (12-cup) Bundt pan, preferably nonstick, with cooking spray.
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3
Spread walnuts in a small baking pan and toast in the oven until fragrant, 4 to 6 minutes.
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4
Let cool.
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5
Place walnuts, whole-wheat flour, all-purpose flour, baking powder, baking soda and salt in a food processor; process until walnuts are finely ground.
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6
Combine buttermilk, oil, rosemary, vanilla and lemon zest in a glass measuring cup.
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7
Place eggs, egg whites and sugar in a large mixing bowl.
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8
Beat with an electric mixer on high speed for 5 minutes.
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9
The mixture should be thickened and pale.
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10
With a rubber spatula, alternately fold the dry ingredients and buttermilk mixture into the egg mixture, making 3 additions of the dry and 2 additions of liquid.
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11
Scrape the batter into the prepared pan, spreading evenly.
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12
Bake until the top springs back when touched lightly and a toothpick inserted in the center comes out clean, 35 to 40 minutes.
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13
Let cool in the pan on a wire rack for 5 minutes.
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14
Loosen the edges and turn the cake out onto the rack to cool completely.
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15
To serve, place cake on a plate and dust with confectioner's sugar and serve with fresh berries and a dollop of sweetened whipped cream.
