Preheat your oven to 375°F and line a small loaf pan with parchment paper for easy removal.
Finely dice the yellow onion and mince the garlic clove until very small.
In a large mixing bowl, combine the ground beef, egg, quick-cooking oats, onion, garlic, sea salt, black pepper, and dried oregano.
Gently mix the ingredients by hand until just combined, being careful not to overwork the meat which can lead to a tough texture.
Press the meat mixture evenly into the prepared loaf pan and smooth out the top with a spatula.
In a small bowl, whisk together the tomato paste, balsamic vinegar, and maple syrup to create a thick glaze.
Spread the tomato glaze evenly over the top of the meatloaf using the back of a spoon.
Bake for 40 to 45 minutes, or until the internal temperature reaches 160°F when measured with a meat thermometer.
Remove from the oven and let the meatloaf rest for 10 minutes before slicing to ensure the juices redistribute throughout the loaf.