Sauté the olive oil in a large stock pot or Dutch oven. Toss in the chopped onion and minced garlic, cooking until fragrant and the onions turn translucent.

Add the ground beef and Italian sausage. Cook until browned and no longer pink, then drain any excess fat.

Stir in the marinara sauce, diced tomatoes, chicken broth, Italian seasoning, red pepper flakes (if using), salt, and pepper. Bring it to a rolling boil.

Add the broken lasagna noodles. Let it simmer for about 15 minutes, stirring frequently to prevent sticking and clumping.

Before serving, throw in the spinach and let it wilt. Give it a taste and adjust the spices or broth as needed. Serve with some ricotta or cottage cheese if desired.