Rub the meat cubes with 2 tablespoons paprika and ½ cup olive oil. Cover and refrigerate overnight, if possible, or let marinate 2 hours at room temperature.
Heat 2 tablespoons oil in a large sauté pan over medium heat. Add the pancetta and cook until rendered and halfcooked, 10 to 15 minutes; transfer to a large casserole with a slotted spoon. Add as many beef cubes to the sauté pan as will comfortably fit (overcrowding will cause the beef to steam, rather than brown) and brown on all sides over high heat; transfer to the casserole with the pancetta. Repeat with the remaining beef cubes, adding 1 to 2 tablespoons oil to the pan as needed for each batch. Add the onions to the sauté pan and cook over medium heat until translucent, 7 to 10 minutes. Add the garlic, cayenne, and the remaining ¼ cup paprika and cook 5 minutes longer. Transfer to the casserole with the beef.
Add the wine and diced tomatoes with juices to the casserole and heat to boiling. Reduce the heat and simmer covered until the beef is tender, about 2 hours. Season to taste with salt and pepper, and more cayenne and paprika if you like. Serve with pappardelle, mashed potatoes, or polenta.