Combine brown sugar and steak seasoning. Add sugar mixture to the skillet and stir.
When the meat has browned, add onion, peppers, vinegar and Worcestershir sauce to the skillet. Reduce heat to medium and cook for 5 minutes.
Add tomato sauce and paste to pan. Stir to combine. Reduce heat to simmer and cook mixture for 5 minutes longer.
Using a large spoon or ice cream scoop, pile sloppy meat onto toasted, buttered bun bottoms and cover with bun tops. Have plenty of napkins on hand!