In a large skillet over medium-high heat, heat oil until shimmering. Cook onion and bell pepper, stirring occasionally, until softened and slightly golden, 10 to 15 minutes.
Add the garlic and cook for 1 minute until fragrant.
Stir in the chili powder and tomato paste cooking until the mixture has turned a deep burgundy color.
Add the ground beef to the pan and cook until browned and no longer pink, approximately 5-7 minutes.
In a bowl, whisk together the Worcestershire sauce, apple cider vinegar, yellow mustard, brown sugar dan tomato sauce. Pour the sauce mixture over the ground beef and stir to combine.
Turn the heat to low and simmer for 10 minutes.
Divide beef mixture among buns and serve.
Video
Notes
Leftover Sloppy Joe will last in the refrigerator for up to 5 days.