In a large skillet over medium heat, cook the ground beef until it begins to brown. Stir in the onion, garlic powder, and salt and cook for 7 minutes, or until beef has browned and onion has softened.
Stir in the coconut aminos and cream cheese until incorporated. Turn off the heat and set aside.
Spray a 9x13 casserole dish with cooking spray. Spread the beef mixture in the bottom of the casserole dish.
In a small mixing bowl, whisk together the eggs and heavy cream. Pour the heavy cream mixture over the meat mixture evenly.
Sprinkle the Big Mac Casserole with the shredded cheese and place in the oven to bake for 20 minutes.
Remove the casserole from the oven and sprinkle with sesame seeds (if using). Return the casserole to the oven and bake for 10 minutes or until the cheese is melted and casserole is cooked through.
While the casserole is baking, make the Big Mac Sauce. Mix the mayonnaise, ketchup, pickle relish, garlic powder, and smoked paprika together until combined. Store in the refrigerator until ready to serve.