Preheat oven to 350. combine flour, cornmeal, cinnamon, nutmeg, and salt in medium bowl., Cream butter and brown sugar in large bowl. Mix in egg yolk and vanilla. Mix in dry ingredients. Form dough into 1-inch balls. Place on ungreased cookie sheets and make depression in center using thumb. Bake 10 minutes. Fill depressions with jam and return to oven for 8 minutes.