Heat a large deep skillet or Dutch oven over medium-high heat. Add the ground beef and diced yellow onion. Cook for 5 to 6 minutes, breaking the beef apart with a wooden spoon, until browned and cooked through. Drain off any excess grease if desired.

Stir in minced garlic, tomato paste, smoked paprika, garlic powder, onion powder, kosher salt, and black pepper. Sauté for 1 to 2 minutes until the tomato paste darkens to a deep brick-red and turns fragrant.

Pour in the beef bone broth and uncooked pasta shells. Stir well, using your spoon to scrape up all browned bits from the bottom of the skillet. Bring the liquid to a lively boil.

Once boiling, reduce the heat to medium-low, cover with a tight-fitting lid, and simmer for 9 to 11 minutes, stirring occasionally, until the pasta shells are perfectly al dente and most of the liquid has absorbed.

Remove the lid and turn the heat to low. Pour in the heavy cream, stirring continuously until a glossy sauce forms around the shells.

Gradually fold in the freshly shredded sharp cheddar cheese and grated Parmesan cheese in two batches, stirring until completely melted, creamy, and velvety. Remove from heat, let rest for 2 minutes to thicken, garnish with chopped parsley, and serve hot!