Finely chop the onions. Cut the red pepper into small cubes. Chop the rosemary. Cut the beef into strips.
Season the beef strips with salt and pepper. In a large frying pan over high heat, brown the beef for 2-3 minutes until seared on all sides. Remove from the pan and set aside.
If needed, add a small amount of butter to the pan. Reduce heat to medium. Add the onions and sauté for 3-4 minutes until softened. Season lightly with salt. Add the red pepper cubes and sauté for 2 minutes. Stir in the tomato paste and chopped rosemary, cook for 1 minute. Pour in the white wine to deglaze the pan. Return the beef to the pan. Simmer over medium heat for 45 minutes until the beef is tender.
Stir in half of the crème fraîche and heat through for 1-2 minutes. Serve with rice, pasta, or spaetzle, topped with the remaining crème fraîche.