In a large, oven-proof skillet over high heat, add the ground beef and cook, crumbling as it cooks, until browned, around 5 minutes. Drain excess fat.

Add the Ragu sauce and water and stir to combine. Season with salt and pepper to taste, then bring mixture to a boil, add the ziti pasta and return to a boil. Cover, reduce heat to low, and allow to simmer for 15-20 minutes, or until the pasta is tender, stirring occasionally.

Preheat oven to 500 degrees. While the pasta is cooking, add the ricotta, mozzarella, parmesan, and egg to a small bowl and whisk thoroughly to combine.

When the pasta is tender, stir half of the cheese mixture into the sauce, then layer the remaining on top. Place in the oven and allow to bake for 5-10 minutes, or until the cheese on top starts to melt and brown. Remove from oven and serve immediately.