- PREHEAT oven to 350F. Position racks in top and bottom thirds of oven. Line 2 baking sheets with parchment.
- WHISK ground almonds with rice flour, cornstarch, ½ cup icing sugar, lemon zest, baking powder and salt in a large bowl. Knead in butter and vanilla until dough forms.
- SCOOP dough and roll into 1-in. balls, then arrange on prepared sheets, 1 in. apart. Press down on cookies lightly with a fork.
- BAKE in top and bottom thirds of oven, switching and rotating sheets halfway through, until cookie edges crack, 17 to 20 min. Dust cooled cookies with 2 tbsp icing sugar.
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