Preheat the Oven: Heat the oven to 350°F.
Sauté the Onion: Place a large skillet over medium heat and add the extra virgin olive oil and finely diced red onion. Cook for 5–6 minutes, stirring as needed, until the onion is soft. Wilt the Spinach: Add the roughly chopped fresh spinach to the skillet with the softened onion. Cook until the spinach has wilted, then remove the mixture from the heat and set it aside. Combine the Meatloaf Mixture: In a large bowl, combine the ground lamb, egg, almond flour, ¼ cup ketchup, dried oregano, dried mint, sea salt, pepper, and the cooked onion-and-spinach mixture.Mix thoroughly with a large spoon or your hands until the ingredients are evenly incorporated. Shape the Meatloaf: Press the mixture firmly into a loaf pan. Alternatively, shape it into a loaf and place it on a rimmed baking sheet. Prepare the Glaze: Stir together the remaining ¼ cup ketchup and 1 tbsp maple syrup until evenly combined.
Apply the Glaze: Spread the ketchup-maple mixture evenly over the top of the meatloaf.
Bake the Meatloaf: Place the meatloaf in the preheated 350°F oven and bake for 45–50 minutes, or until the center is set and no longer pink.
Check the Temperature: For a reliable doneness check, insert a meat thermometer into the center of the loaf. Remove the meatloaf when the thermometer registers 160°F. Rest Before Slicing: Allow the cooked meatloaf to cool for 5–10 minutes before slicing.
Slice and Serve: Slice the meatloaf directly in the loaf pan, or carefully remove it and transfer it to a cutting board before slicing.