1. Cookies: Preheat oven to 350 degrees. In a food processor, pulse cashews with 1/2 cup flour until nuts are very finely ground. In a bowl, whisk to combine cashew mixture with remaining 1 1/2 cups flour, the baking powder, salt, zest, cardamom, and cayenne pepper.

2. In a separate bowl, beat butter and brown sugar with an electric mixer on medium-high speed until fluffy, 3 to 4 minutes. Add lime juice and egg, and beat until combined. Reduce speed to low; add flour mixture and beat just until combined.

3. Divide dough into quarters, and shape into 3/4-inch square logs. Chill 30 minutes. (Dough may be wrapped in plastic and refrigerated up to 1 week or frozen up to 3 months; bring to room temperature before proceeding.) Slice logs to form 3/4-inch cubes. Press top of each cube gently to round corners; place cubes on parchment-lined baking sheets, spacing 1 1/2 inches apart. Bake, rotating sheets halfway through, until golden on edges and bottoms, 13 to 15 minutes. Let cookies cool completely on wire racks.

4. Lime Glaze: In a small bowl, whisk to combine confectioners' sugar and lime juice until smooth. Use immediately.

5. Brush the top of each cookie with glaze. Sprinkle about 1/4 teaspoon spice blend on top of each cookie. Let set 30 minutes. Cookies can be stored in an airtight container at room temperature up to 3 days.