Preheat your oven to 350 degrees f and line a 5×9 loaf pan with parchment paper.
Heat a large skillet over medium heat. Add the butter and once melted, stir in the onion, celery, carrot, garlic, and Italian seasoning. Sauté, stirring frequently, for about 5 minutes.
In a large bowl, add the ground beef, sausage meat, egg, mozzarella, parmesan, almond flour, and a pinch of sea salt and pepper.
Once the veggies are done cooking, transfer them to the large bowl with the meat. Stir very thoroughly to combine everything well.
In a small bowl, whisk the mustard together with the ketchup.
Transfer the meat mixture to your prepared pan, then spread your ketchup/mustard mixture over the meat.
Bake for 45-50 minutes, or until the internal temperature reaches 160F.
Allow it to rest for 10 minutes before slicing and serving.
Serve your meatloaf slices over mashed potatoes and steamed broccoli.
Meatloaf stays good in the fridge if sealed well for up to 4 days. Reheats GREAT which makes this ideal for future lunches.
Enjoy!