Heat oven to 350°. Line a 9 x 5 x 3-inch loaf pan with nonstick foil. Set aside. In a medium bowl, whisk cornmeal, flour, flaxseed meal, baking powder and salt. In a large bowl, whisk oil, yogurt and eggs. Add other ingredients as directed in each variation that follows.
Mix dry ingredients into wet ingredients. Fold in any extras. Transfer batter to prepared pan and bake as directed. Cool completely on a wire rack.