In a medium bowl, using a handheld electric mixer, beat the butter and sugar at medium speed until light and fluffy, about 2 minutes.
Sift the flour with the curry powder, salt, paprika, turmeric, chili powder and black and cayenne peppers. Gradually add the dry ingredients to the butter and beat until blended.
Scrape the shortbread dough out onto a sheet of plastic wrap or parchment paper and pat it into a log 1 1/4 inches in diameter. Pat the log into a rectangle and wrap it up. Refrigerate until firm, about 1 hour.
Preheat the oven to 350°. Slice the dough 1/4 inch thick and arrange on 2 parchment-lined baking sheets. Prick the top of the shortbreads all over with a fork and bake for 20 minutes, or until golden. Slide the parchment onto a wire rack and let the shortbreads cool.
MAKE AHEAD The cooled shortbreads can be stored in an airtight container at room temperature for up to 1 week or frozen for up to 1 month.
