1 1/2 cups pine nuts (about 7 ounces)
1 cup sugar
1/4 cup (packed) almond paste, crumbled
1 1/2 teaspoons grated lemon peel
3/4 teaspoon vanilla extract
3 large egg whites
1 1/3 cups all purpose flour
1/2 teaspoon baking powder
1/4 teaspoon salt
1/2 cup powdered sugar (for dusting)
Preheat oven to 350 F. Butter 2 large baking sheets. Using on/off turns, blend 3/4 cup pine nuts and next 4 ingredients in processor until crumbly mixture forms. Transfer mixture to large bowl; add egg whites. Using electric mixer, beat until mixture is smooth. Whisk flour, baking powder, and salt in small bowl to blend. Add to pine nut mixture; beat until smooth (dough will be soft and sticky).
Place remaining 3/4 cup pine nuts in shallow bowl. Spoon generous tablespoonful dough into pine nuts in shallow bowl, coating 1 side of dough with pine nuts. Using floured fingertips, transfer dough to prepared baking sheet, pine nut side up. Smooth edges of dough to form even round. Repeat with remaining dough, flouring fingertips as needed to prevent sticking and spacing cookies 2 inches apart on prepared baking sheets.
Bake cookies 1 baking sheet at a time until golden, about 20 minutes. Cool completely. Dust with powdered sugar, transfer to plate, and serve. (Cookies can be made 1 day ahead. Store in airtight container at room temperature.)
*Almond paste is available at specialty foods stores and in the baking-products section of most supermarkets.