Preheat oven to 400. Coat a large baking dish with olive oil. Spread the salsa on the bottom of the prepared baking dish; set aside.
Heat the 2 tablespoons of olive oil in a large skillet over medium heat. Add ground beef and seasonings (garlic powder through oregano); cook, breaking meat up with a wooden spoon, until almost cooked through. Add onion and bell pepper; cook until soft. Stir in tomato sauce then bring mixture to a simmer and cook for 3 to 4 minutes; remove from heat and set aside.
Fill hollowed-out zucchini with meat mixture, packing as tightly as possible. Place stuffed zucchini in prepared baking dish and sprinkle with cheese. Cover with foil and bake for 25 minutes. Remove the foil and bake for 10 minutes more or until golden brown and cooked through.
Sprinkle with chopped cilantro and serve.