Preheat oven to 375°F and lightly grease a 12-cup muffin tin.
In a large mixing bowl combine the rolled oats, dried minced onion, and milk. Let sit for 2–3 minutes to soften.
Add the ground beef, egg, ketchup, coconut aminos, garlic powder, salt, and pepper. Mix gently until just combined.
Divide the mixture evenly between the muffin cups, filling each almost to the top.
OPTIONAL: In a small bowl mix ketchup, brown sugar, and mustard. Spread about 1 teaspoon on top of each meatloaf muffin.
Bake for 18–22 minutes, or until the internal temperature reaches 160°F.
OPTIONAL: Broil the muffins for 2-3 minutes to caramelize the glaze, just keep an eye on them so that they don't burn.
Let the meatloaf muffins rest for 5 minutes before removing from the pan and serving.