Add vegetables (diced onion, green pepper, celery, and carrots) and season with salt and pepper. Cook until translucent, about 10 minutes.
Remove vegetable mixture from heat and add tomato paste, liquid aminos, and spices. Season generously with salt & pepper; mix until combined. Cool for 5-10 minutes.
While the vegetable mixture cools, add eggs to a large mixing bowl; whisk. Add oatmeal, ground beef, and vegetables to the mixing bowl. Mix until well combined; I prefer using gloved hands.
Press meat and vegetable mixture into a 9-inch x 13-inch baking pan. Top with ketchup.
Bake in a preheated 375 degree oven for 50-60 minutes until bubbly and internal temperature is 160 F.
Nutrition Facts
Per serving (~3-inch x 3-inch square): 260 calories, 11 g fat, 10 g net carbohydrates, 28 g protein