Preheat your oven to 375°F (190°C).
In a skillet over medium heat, sauté the diced onion and bell pepper in olive oil until they are tender and slightly caramelized.
Place the cooked chicken breast in a bowl and shred it with two forks, then toss with the garlic powder, cumin, and half of the chili powder.
In a small saucepan, combine the tomato puree with the sea salt, black pepper, and the remaining chili powder, simmering for 5 minutes to develop the ranchero flavor.
Briefly warm the corn tortillas in a dry pan or microwave to make them flexible.
Divide the shredded chicken and sautéed vegetables evenly between the two tortillas, roll them up tightly, and place them seam-side down in a small baking dish.
Pour the warm ranchero sauce over the top of the tortillas and sprinkle with the shredded cheddar cheese.
Bake for 12 to 15 minutes until the cheese is melted and the edges of the tortillas are slightly crisp.