Brown the Onion and Beef: Heat the olive oil in a large, deep skillet over medium-high heat. Add the onion and ¼ teaspoon of the salt. Cook for 3-4 minutes, until just beginning to soften.
Add the beef and ¼ teaspoon of salt, breaking into small crumbles. Cook until no pink remains, about 5-6 minutes, stirring frequently. Drain any excess fat.
Season: Add the garlic and tomato paste. Cook for 1 minute, stirring constantly, until the tomato paste darkens slightly.
Add the Worcestershire sauce, garlic powder, onion powder, smoked paprika, ¼ teaspoon of salt, and pepper and stir to coat the beef evenly.
Add the Liquids: Pour in the beef broth and milk or half-and-half and stir to combine, scraping up any browned bits from the bottom of the pan.
Add the Pasta: Add the dry elbow macaroni and stir to submerge. Bring to a boil over medium-high heat, then reduce to a steady simmer.
Cook, uncovered, for 10-12 minutes, stirring every couple of minutes to prevent sticking, until the macaroni is tender and has absorbed most of the liquid.
Stir more often the first couple of minutes to make sure the pasta doesn’t stick to the bottom of the pan. If the pan starts to dry out before the pasta is cooked add a splash more stock.
Add the Cheese: Remove from heat. Add the shredded cheddar in two additions, stirring between each until fully melted and the sauce is creamy and smooth.
Taste for seasoning and adjust with salt and pepper as needed.
The sauce thickens as it sits. If reheating, add a splash of broth or milk to loosen it back up.
Notes
If you want to veg it up, stir in 1 cup of frozen peas, corn, or chopped spinach during the last 2 minutes of cooking. The frozen vegetables cook through in the residual heat without needing extra time on the stove!
For the smoothest sauce, I recommend using freshly grated cheddar (rather than bagged, pre-shredded), since pre-shredded contains an anti-caking agent that prevents it from melting into a perfectly smooth sauce. Adding the cheese off the heat will also help it to melt right in without separating.