Warm a large, deep skillet over medium heat. Add the olive oil—it should shimmer lightly.

Toss in the chopped onion and a pinch of salt. Cook 3–4 minutes until soft, stirring so it doesn’t stick.

Crumble in the ground beef and cook until no pink remains (about 5 minutes). Drain excess fat if needed—leave a tablespoon for flavor.

Stir in garlic and tomato paste; then add diced tomatoes, beef broth, Italian seasoning, and red pepper flakes. Give it a good stir.

Bring to a boil, then stir in the elbow macaroni. Cover, reduce heat, and simmer 12–14 minutes—stir once halfway through.

Stir in frozen peas (or spinach), then sprinkle mozzarella and Parmesan. Cover until cheese melts.

Let the casserole sit covered for 5 minutes. Scatter chopped basil or parsley across the top before serving.