Heat olive oil in a large skillet, over medium-high heat.
Add onion and sauté until translucent.
Add meat, season with salt and chili powder, and cook until is fully cooked. (Drain any liquid before adding the rest of the ingredients.)
Add the next 6 ingredients (mustard through tomato sauce). Stir until well combined. Cook for approximately 5 to 10 minutes, uncovered.
Serve on warm hamburger buns.