1. Stir together flour, salt and poppy seeds. Set aside.
2. In large mixing bowl beat butter, sugar, egg yolks, lemon peel and vanilla until well combined. Add flour mixture, mixing well. Portion and shape dough into 1-inch balls. Roll in Kellogg's Corn Flakes® cereal. Place on ungreased baking sheets, about 2 inches apart. Flatten slightly.
3. Bake at 375°F about 8 minutes or until edges are lightly browned. Remove from baking sheets and cool or wire racks. Store in airtight container.