Heat a large skillet with tall sides (this is my skillet, pictured), or a dutch oven, over medium-high heat.
Add the oil to the hot skillet, along with the diced onions and peppers. Cook until softened and translucent. Add garlic in the final minute so it doesn’t burn.
Push the onions and peppers to the outside of the pan, clearing a spot in the middle. Add the ground beef and cook through.
While the beef is browning, mix the sauce.
Add all the sauce ingredients to a mixing bowl (tomato sauce through salt) and stir well to combine.
If there's a lot of fat in the skillet (this will depend on your ground beef), drain the fat before proceeding on...Once the beef is cooked through, stir in the sauce. Simmer over low heat for 20 minutes. I cover the skillet and check on the mixture every few minutes, stirring if needed, to prevent a particular area from burning/sticking.
Serve on fresh buns. I also like to serve these with sauerkraut.