Mix the seasoning. In a small bowl, whisk together the brown sugar, smoked paprika, dried minced onion, cumin, garlic powder, salt, and black pepper. Break up any brown sugar clumps with the back of a spoon. Set aside.
Brown the beef. Heat a large skillet over medium-high heat. Add the ground beef and cook for 5–7 minutes, breaking it apart with a wooden spoon, until no pink remains. If using onion and bell pepper, add them halfway through browning. Drain excess grease.
Add the wet ingredients. Stir in the tomato sauce, water, apple cider vinegar, and mustard until smooth.
Stir in the seasoning. Sprinkle the full dry mix over the meat and stir until everything is fully combined.
Simmer. Reduce heat to medium-low and simmer uncovered for 10–15 minutes, stirring occasionally, until the sauce thickens to your desired consistency.
Serve. Spoon generously onto toasted hamburger buns, top with shredded cheese if desired, and serve warm.