In a large skillet, brown the beef over medium high heat, breaking up any large pieces until about halfway cooked; 4 minutes or so.
Add the onions, garlic and bell pepper and cook with the beef until the vegetables soften and no pink remains in the meat. 3 to 4 minutes more.
Remove from the heat and drain any excess grease and season with salt. Stir to combine.
Return to low heat and add the ketchup, water, chili powder, brown sugar, salt, pepper and mustard. Stir to combine and simmer until the liquids thicken and evaporate slightly--5 to 6 minutes. Serve warm.