Sift together flour, soda, sugar, and salt; stir in cornmeal. Combine eggs, vinegar, and shortening; add to dry ingredients, stirring just until moistened.
Heat a well-greased 9-inch cast-iron skillet in a 400° oven for 3 minutes. Spoon batter into hot skillet. Bake at 400° for 30 minutes or until lightly browned.