Cheesy Beef Loaf Stuffed With Caramelized Onions & Mushrooms (Keto & Low-Carb Friendly)

Ingredients & Measurements for Cheesy Beef Loaf stuffed with Caramelized Onions & Mushrooms:

For the Filling:
3 tbsp olive oil
1 large onion, julienne sliced
1/2 tsp salt
1/2 tsp black pepper
300 grams diced mushrooms
For the Beef Mixture:
450 grams (1 pound) minced beef
1 egg
1 tsp Himalayan salt
1 tsp black pepper
1 tsp garlic powder
1 tsp paprika
1 tsp ground coriander

Grated cheddar cheese (for two layers)

For the Topping:
Tomato paste seasoned with salt and garlic powder (to taste).