In a large skillet over medium heat, brown the ground beef until fully cooked. Drain any excess fat. Add the chopped onion and green bell pepper, cooking until the vegetables are soft, about 5-7 minutes. Stir in the taco sauce and enchilada sauce, mixing well to combine. Let this simmer for a few minutes to meld the flavors.
In a mixing bowl, combine the ricotta cheese with the egg. Mix until smooth and well blended.
Preheat your oven to 375°F (190°C). In a 9x13 inch baking dish, start layering. Begin with a scoop of the beef and veggie mixture, followed by three lasagna noodles placed side by side. Next, spread half of the ricotta mixture over the noodles, followed by a sprinkle of cheddar cheese. Repeat this process one more time, ending with a layer of the beef mixture and a generous topping of cheddar cheese.
Cover the baking dish with aluminum foil and bake for 25 minutes. Then, remove the foil and bake for an additional 10-15 minutes, or until the cheese is bubbly and slightly golden.
Once out of the oven, let your taco lasagna sit for about 10 minutes to set. Top with chopped cherry tomatoes, green onions, cilantro, and sliced avocado before serving.