Preheat the oven to 350 degrees F (175 degrees C).

Mix together ground beef, mushroom, onion, eggs, 1 teaspoon salt, and 1/2 teaspoon pepper in a large bowl until combined. Press about 3/4 of the meat mixture into the bottom and up the sides of a loaf pan, leaving a well in the middle.

In another large bowl, combine the cream cheese, 1 cup Cheddar cheese, garlic powder, 1 teaspoon salt, and remaining 1/2 teaspoon pepper. Press cream cheese mixture into the well of the meatloaf. Cover with remaining meat mixture, pressing along the edges to seal. Cover loosely with aluminum foil.

Bake for 30 to 35 minutes or until an instant-read thermometer inserted into the center reads 160 degrees F (70 degrees C). Remove from the oven, and turn oven to broil.

Remove foil. Brush the top of the meatloaf with keto BBQ sauce, and sprinkle with 2 tablespoons grated Cheddar.

Place meatloaf in the middle rack under the broiler and cook until the sauce is bubbly and cheese is melted, 2 to 3 minutes.