Preheat oven to 375 degrees. Grease baking sheet or line with parchment paper. Place butter and sugar in mixing bowl and beat until light and smooth. Beat in egg and vanilla. In separate bowl, combine flour, nuts, cinnamon and salt. Combine all ingredients. With moistened finger tips, pinch off pieces of dough and roll between your palms to form one-inch balls. Place on prepared sheet, spacing about 1-½ inches apart. Press your thumb into the center of each cookie. Fill the indentation with blueberry fruit preserves. Bake until golden, 8-10 minutes or until the cookies are lightly browned on the top and slightly darker on the bottom.