In a pan set over medium-high heat, heat the oil and sauté the onion. Add the meat and chili powder and continue to cook, crumbling the meat with a wooden spoon. Cook until meat is golden, stirring often.
Add the remaining ingredients and continue to cook for approximately 10 minutes over low heat. Add a bit of water if needed.**
When ready to serve, reheat the meat, toast the buns, and garnish each with the meat mixture. Serve with the toppings of your choice.
*You can replace the ground beef with ground chicken or turkey. For a vegetarian version, opt for ground tempeh or tofu.
**The meat mixture can be made ahead of time and reheated while camping.