Preheat oven to 350° F.

Beat butter with an electric mixer on medium speed for 30 seconds. Add brown sugar and baking powder and beat until combined.

Add egg yolk and vanilla until combined, then add cornmeal.

Beat in as much of the flour as you can with the mixer. Using a wooden spoon, stir in any remaining flour.

Shape dough into 3/4-inch balls and place 1 inch apart on an ungreased cookie sheet. 

Lightly press the tip of your thumb into the center of each ball of dough and fill each center with about 1/8 teaspoon of pepper jelly.

Bake for about 10 minutes or until bottoms are lightly browned. Cool on cookie sheet for 1 minute. Transfer cookies to a wire rack; let cool completely.