Brown the ground beef in a large skillet, drain the grease, and set the meat aside.
In the same skillet, melt butter over medium-high heat and sauté onions until translucent.
Add all sauce ingredients: tomato sauce, ketchup, brown sugar, mustard, Worcestershire, vinegar, and seasonings.
Simmer for 5–7 minutes.
Stir in the cooked ground beef and heat through.
Butter the inside of each bun and toast on a griddle until golden.
See full steps with tips & photos → https://theboatshedcafe.com/sloppy-joe-sandwiches-2/