In a medium bowl, using a fork, stir flour with baking powder, salt and peel. In a large bowl, using an electric mixer, beat butter with sugar. Beat in egg, vanilla and juice. Finely chop 1 large seeded jalapeno. Stir into flour mixture along with 1 tbsp (15 mL) ground cumin.
In a large bowl, using an electric mixer, beat butter with sugar. Beat in egg, vanilla. Using a wooden spoon, gradually beat in flour mixture just until it can be formed into a ball. Shape into 3 6-in. (15-cm) triangular logs or 3 8-in. (20-cm) round logs. Place 3 tbsp (45 mL) cumin seeds in a pie plate. Press sides of each log into seeds. Wrap separately with plastic wrap and refrigerate until firm, at least 1 hour or up to 1 week.
To bake, preheat oven to 350F (180C). Spray or oil a large baking sheet. Slice logs into rounds 1/3 in. (0.7 cm) thick. Place about 2 in. (5 cm) apart on baking sheet. Bake in centre of preheated oven until cookie edges are golden, 8 to 10 min. Remove cookies to a rack to cool completely. Repeat with remaining dough. Store in an airtight container in the refrigerator up to 1 week or freeze up to 1 month.