Prepare the Pasta Shells:
Bring a large pot of salted water to a boil. Add jumbo pasta shells and cook according to package directions until al dente. Drain and set aside.
Make the Taco Filling:
Heat a large skillet over medium heat and add ground beef. Cook until browned, breaking up the meat as it cooks.
Drain any excess grease and add the diced onions and bell peppers. Cook until softened, about 3 minutes.
Add taco seasoning, canned tomatoes with green chilies, and black beans (if using). Mix well and cook for another 2-3 minutes. Remove from heat and stir in 1 cup of shredded cheese.
Prepare the Queso Sauce:
In a medium saucepan over low heat, warm the evaporated milk.
Gradually add shredded cheese, stirring continuously until the cheese is melted and the sauce is smooth.
Add paprika, garlic powder, salt, and pepper. Stir until combined.
Assemble and Bake:
Preheat your oven to 350°F (175°C).
Spread a thin layer of queso sauce on the bottom of a 9x13-inch baking dish.
Stuff each shell with the taco mixture and place it in the prepared baking dish.
Pour the remaining queso sauce over the shells, covering them evenly.
Cover with foil and bake for 20 minutes. Remove the foil and bake for an additional 10 minutes or until bubbly.
Garnish and Serve:
Remove from the oven and let cool for a few minutes.
Garnish with chopped cilantro, green onions, and diced tomatoes. Serve with a dollop of sour cream if desired.