Bring a large pot of salted water to a boil and cook pasta shells until al dente; drain and set aside.
In a large deep skillet or Dutch oven over medium-high heat, brown the ground beef and diced onions until the meat is fully rendered and onions are translucent.
Drain the excess lipid content from the pan, leaving approximately one tablespoon for flavor.
Incorporate the minced garlic and tomato paste; cook for 90 seconds until the paste darkens in color.
Deglaze the pan with beef broth, then stir in the tomato sauce, oregano, smoked paprika, salt, and pepper.
Reduce heat to medium-low and simmer the sauce for 5 to 7 minutes to allow flavors to integrate.
Stir in the heavy cream and shredded cheddar cheese, whisking continuously until the cheese is fully emulsified into the sauce.
Add the cooked shells to the skillet and toss to ensure the sauce fills the cavities of the pasta.
Heat for an additional 2 minutes until the sauce achieves a thick, glossy consistency.