Make the taco seasoning: in a small bowl combine salt and pepper, oregano, chili powder, cumin, garlic powder, and onion powder.
Heat 1 tablespoon oil in a large skillet over medium-high heat.
Add the diced onion and bell pepper and cook, stirring, until softened about 5 minutes.
Add the ground chicken, minced garlic, half of the chopped cilantro, and the taco seasoning; break up the meat and cook over medium-high heat until no longer pink, about 8–10 minutes.
Stir in 1/2 cup salsa and 1–2 tablespoons water, reduce heat to medium, and simmer for about 5 minutes so the chicken absorbs the sauce.
Turn off the heat and stir in the remaining cilantro.
Preheat the oven to 400°F (200°C). Arrange the soft tortillas in a single layer on a baking sheet and sprinkle shredded cheddar evenly over each tortilla.
Bake the tortillas until the cheese is fully melted, about 6–8 minutes. Remove from oven, place a hard taco shell on top of each melted-cheese tortilla, and press the soft tortilla sides around the hard shell to form a sturdy cheesy shell.
Assemble tacos: fill each shell with a generous portion of the ground chicken mixture.
Top with diced avocado, cherry tomatoes, scallions, extra cilantro, sliced jalapeños, and a lime wedge to serve.
