Preheat your oven to 375°F (190°C) and line a small baking dish with parchment paper.
Finely dice the yellow onion and mince the garlic clove.
In a small non-stick skillet over medium heat, sauté the onion and garlic for 3-4 minutes until softened and translucent, then let cool slightly.
In a large mixing bowl, combine the lean ground beef, egg, almond flour, sautéed vegetables, sea salt, black pepper, and dried oregano.
Gently mix the ingredients by hand until just incorporated, taking care not to overwork the meat to maintain a tender texture.
Shape the mixture into a uniform loaf shape and place it into the prepared baking dish.
In a small ramekin, whisk together the unsweetened ketchup, apple cider vinegar, and smoked paprika to create the glaze.
Spread the tomato glaze evenly over the top and sides of the meatloaf using a spoon or pastry brush.
Bake for 25 to 30 minutes, or until the internal temperature reaches 160°F (71°C).
Remove from the oven and let the meatloaf rest for 5 minutes before slicing to allow the juices to redistribute.