Heat a large pot over medium heat and add the ground beef, breaking it up with a wooden spoon. Add the chopped onion and continue cooking for 5-8 minutes, until the ground beef is no longer pink and the onion is translucent.
Add the minced garlic and cook for 1 minute until fragrant.
Drain the meat. (I usually do this by setting a colander over a bowl.) Return the beef to the pot.
Turn the heat on to medium again. Add the flour, salt, paprika, smoked paprika, oregano, cumin, and chili powder. Stir it together and cook for one minute.
Add the beef broth, Rotel, tomato sauce, and drained beans. (Don't drain the Rotel, add all those juices in.) Turn the heat up to high and bring to a boil.
Add the elbow macaroni. If you are using Velveeta, roughly chop it and add it in along with the noodles. Stir occasionally for about 8 minutes until the noodles are al dente and the Velveeta has melted.
If you are using shredded cheddar cheese, add it after the noodles are al dente. Add the cheese and turn off the heat. Stir until melted.
Chili Mac is nothing without the garnishes: crushed tortilla chips, sour cream, shredded cheddar cheese, chopped white onions, avocado...the sky is the limit here.