Peel and cut the plantains into chunks, then boil until soft, about 15-20 minutes. Drain and mash them with salt, pepper, butter, and milk until smooth. Mix in the cheese if you're adding it then set aside.
In a pan over medium heat, cook the sofrito with onion, garlic, and bell peppers until softened. Add the ground beef, breaking up large chunks with a spoon.
Once the meat starts to brown, season with sazón, adobo, oregano, garlic powder, and salt. Stir in the tomato sauce and water, then simmer until most of the liquid has evaporated and set aside.
Preheat the oven to 375°F. In a greased baking dish, first layer the mashed plantain, meat, cheese, then another layer of mashed plantain, meat, and cheese, ending with plantain and cheese on top.
Bake for 30 minutes, then let it cool for 15 minutes before slicing and serving. Buen provecho!