In a large pot or deep skillet, cook ground beef over medium heat until browned. Drain excess grease if needed.

Add diced onion and garlic, cooking until softened, about 2 minutes.

Stir in taco seasoning, diced tomatoes, Rotel tomatoes, and beef broth. Bring to a simmer.

Add spaghetti and press it down into the liquid. Cover and cook on low for 12-15 minutes, stirring occasionally, until pasta is tender.

Remove from heat and stir in shredded cheese and sour cream until creamy and well combined.

Garnish with cilantro and jalapeños if desired. Serve warm.