We call for organic ketchup because it's usually sweetened with sugar, not high-fructose corn syrup. Feel free to toss in chopped fresh herbs for more flavor.
Preheat oven to 375°F.
Combine onion, ground flaxseed, salt, pepper, ground sirloin, grated garlic, and egg in a large bowl. Shape into an 8- x 4-inch loaf on a foil-lined baking sheet coated with cooking spray. Spread ketchup over loaf. Bake at 375°F for 40 minutes or until a thermometer registers 160°F. Cut meatloaf into 8 slices.