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1
Preheat oven to 350F.
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2
Butter a 13- by 9-inch metal cake pan, then line bottom with wax paper.
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3
Butter paper and dust pan with some flour, knocking out excess.
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4
Pulse pistachios in a food processor until finely ground (be careful not to overprocess into a paste).
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5
Add 1 cup flour, baking powder, cardamom, and salt and pulse once or twice to mix.
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6
Combine milk and vanilla in a measuring cup.
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7
Beat together butter and sugar in a large bowl with an electric mixer until pale and fluffy.
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8
Add eggs 1 at a time, beating well after each addition.
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9
Alternately add pistachio flour and milk in batches, beginning and ending with flour, and mix at low speed until just combined.
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10
Spread batter evenly in cake pan and bake in middle of oven until a tester comes out clean, about 20 minutes.
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11
Cool in pan on a rack 10 minutes, then run a thin knife around sides of cake and invert onto rack.
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12
Remove paper and reinvert cake onto a platter.
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13
Cut into squares and serve warm or at room temperature.
