Heat 3 tablespoons olive oil in a large pan over medium-high heat. Lightly coat the lamb liver cubes in flour. Fry for 3-4 minutes, stirring occasionally, until browned. Season with salt, pepper, and paprika powder. Transfer to a plate.
In the same pan, add a splash of oil if needed. Fry the onion, bell peppers, chilli, and garlic over medium-high heat for 5 minutes until softened. Stir in the tomato paste and cook for 1 minute. Pour in the broth to deglaze the pan, scraping up browned bits. Add marjoram and pimentón de la Vera, then stir in the cream. Simmer over medium heat for 5 minutes.
Return the liver to the pan and season with salt and pepper. Simmer for 3-4 minutes for medium doneness, or 5-6 minutes for well-done.