Mix minced beef and pork in a bowl.
Dice the onion and sauté in a pan, then cool.
Combine the meat, sautéed onion, egg, salt, pepper, and almond flour, and mix well.
Shape the mixture into thick patties and grill both sides in a pan.
Melt butter in a pan, add tomato paste, Worcestershire sauce, stevia, water, salt, and pepper to make Keto Hamburg sauce.
Pour the sauce over the grilled hamburger steak to finish.