Cook ground beef on the stovetop until broken up & slightly browned (about 5 minutes). While beef is cooking, chop the red bell pepper & onion. Add ground beef, red pepper, garlic, onion, marinara, fire-roasted tomatoes, chicken broth, and seasonings to the crockpot.
Cook on high for ~4 hours (or low for 8). With 30 minutes left, add lasagna noodles for remainder of cooking time. Serve with desired cheese for topping & enjoy!