Dab the escalopes dry and fry them in hot oil for about 3 minutes on each side. Season with salt and pepper. Remove from the pan and keep warm. Peel and finely dice onion. Drain the tuna.
Sauté the onion and fish in the frying oil. Pour on white wine and cream. Bring to the boil and puree with the cutting stick of the hand mixer. Add green pepper and let it simmer for 5 minutes at low heat.
Season the sauce with lime juice, salt and pepper.