Preheat the oven to 375°F (190°C).
Heat the ovenproof 9-inch skillet over medium-high heat, then add the oil.
Add the diced onion and minced bell pepper and sauté 5–6 minutes until the onion is softened and sweet.
Add the ground beef and minced garlic to the skillet and cook, breaking up the meat, until no pink remains.
Stir in the chili powder, oregano, ground cumin, paprika, garlic powder, onion powder, crushed red pepper flakes, and half of the salt and pepper; reserve about 1/2 teaspoon of the seasoning for later if using the blend.
Add the corn kernels and cook 1–2 minutes to warm them through.
Pour in the diced tomatoes with their juices and simmer until the tomatoes have softened and the sauce thickens slightly, about 3–5 minutes; taste and adjust seasoning with remaining salt, pepper, and reserved taco seasoning.
Stir the cooked spaghetti into the skillet so it is evenly coated with the sauce.
Sprinkle the shredded cheddar evenly over the top and transfer the skillet to the preheated oven; bake 20 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let rest a few minutes, then garnish with dollops of sour cream, sliced jalapeño, minced cilantro, minced green onions, and optional chilli flakes before serving.
