Preheat oven to 400F. Line a large sheet pan with parchment paper.

Heat the olive oil in a large, deep, lidded skillet over medium heat. Once the oil is heated and shimmering, add the sliced onions. Cook, stirring occasionally, until the onions are very soft and caramelizing, 15 to 18 minutes (Note: if the onions start getting too browned, reduce heat to medium low until done caramelizing and add another tablespoon of oil.)

While the onions caramelize, combine the ground beef, coconut aminos, garlic powder, and black pepper in a large bowl. Form about 18 two-tablespoon meatballs with lightly oil clean hands and place on the sheet pan, evenly spaced. Bake until at an internal temperature of 160F, 11 to 13 minutes.

Add the garlic, thyme, salt, and black pepper to the skillet and continue cooking over medium heat until aromatic, 1 to 2 minutes. Add the rice and toast, stirring frequently, until golden brown, 2 to 3 minutes. Pour in the broth, coconut aminos, and ½ cup of water and stir to combine. Bring to a simmer, then reduce the heat to medium low, cover, and cook until the liquid is absorbed and the rice is fluffy, 16 to 19 minutes, stirring halfway through to prevent sticking. If needed, add an additional ½ cup of water if it needs more when you stir halfway through.

Reduce the heat to low, remove the lid, and place the meatballs on top of the rice. Sprinkle the mozzarella on top and cover to melt the cheese, 1 to 2 minutes (or transfer the skillet uncovered to the oven and broil on high for 1 to 2 minutes) . Remove the skillet from the heat, top with chopped parsley, and serve.