In a large skillet over medium-high, heat oil. Add onion and garlic. Cook until onion is translucent, about 3 minutes. Stir in ground beef, cooking until browned, about 5 minutes. Drain fat if necessary.
Add meat mixture to slow cooker crock with tomato puree, tomato sauce, diced tomatoes, bay leaf, paprika, salt and black pepper.
Cover slow cooker and cook on HIGH for 3 1/2 to 4 hours or LOW for 7 to 8 hours.
Meanwhile, cook pasta to al dente according to package directions. Drain and stir into crock with 1 cup shredded cheese.