Measure and mix. In a small bowl, whisk together the ketchup, brown sugar, apple cider vinegar, Worcestershire, Dijon, smoked paprika, garlic powder, onion powder, and black pepper. Add hot sauce or red pepper flakes if you like heat.
Taste and adjust. Dip a spoon in and check the balance.
For more tang, add another 1/2 teaspoon vinegar. For more sweetness, add 1 teaspoon brown sugar. For more depth, add a dash of Worcestershire.
Thicken gently (optional). If you prefer a thicker glaze, simmer the sauce in a small saucepan over low heat for 3–5 minutes, stirring often, until slightly reduced and glossy.
Glaze the meatloaf. Spread about half the sauce over the shaped, uncooked meatloaf before it goes in the oven.
This helps it set and caramelize.
Mid-bake refresh. About 15–20 minutes before the meatloaf is done, brush on another thin layer. This builds flavor without burning.
Serve with extra. Warm any remaining sauce and serve on the side for dipping or spooning over slices.