Start by prepping your ingredients. Peel and dice the sweet potatoes into small, uniform 1/2-inch cubes so they cook evenly. Dice the onion, red bell pepper, and mince the jalapeño (if using) and garlic.
Heat the oil in a large skillet over medium-high heat. Add the diced onion and sauté for 2 minutes until it begins to soften.
Add the ground beef to the skillet. Break it apart with a spatula. Add half of the taco seasoning packet, plus salt and pepper. Cook until the beef is browned, about 6-8 minutes. Add the minced garlic and cook for one more minute until fragrant.
Remove the cooked beef mixture from the skillet and set it aside on a plate. (My tip: Don't wipe the skillet! You want to keep those browned bits on the bottom for flavor.)
To the now-empty skillet, add the diced sweet potatoes, diced red bell pepper, minced jalapeño, the can of fire-roasted tomatoes, and the can of green chilis.
Pour in the beef stock and sprinkle in the remaining half of the taco seasoning. Stir everything together well. Bring the mixture to a simmer, then reduce the heat, cover the skillet with a lid, and let it cook for about 15-20 minutes.
Stir occasionally to prevent sticking. The dish is ready for the next step when the sweet potatoes are fork-tender and most of the liquid has been absorbed.
Turn the heat to low. Add the cooked ground beef mixture back into the skillet. Squeeze in the juice of one fresh lime (this brightens all the flavors) and stir everything to combine.
Sprinkle the shredded cheese evenly over the top. Cover the skillet again for just 2-3 minutes, or until the cheese is perfectly melted.
Remove from heat and garnish with fresh cilantro. Serve immediately with your favorite toppings. Enjoy!