In a large oven-safe skillet, add the onions. Cook on medium heat until they are caramelized, or a deep golden brown. This may take 15-20 minutes.
Add 3/4 cup of the bone broth to the skillet with the caramelized onions. Bring to a simmer and let it reduce slightly.
In the same skillet, layer the no-boil lasagna noodles, caramelized onions, chicken, ricotta cheese, mozzarella cheese, spinach, and minced garlic. Repeat layers until all ingredients are used. Pour remaining beef bone broth over top so the lasagna noodles have a liquid to absorb.
Bake in a preheated oven at 375°F (190°C) for 25-30 minutes, or until the cheese is bubbly and golden brown and the lasagna noodles are cooked and soft.
Let the lasagna cool for a few minutes before serving. Enjoy!