Rub tongue with salt or cornstarch to remove slime. Rinse in running water. Blanch in boiling water then peel or scrape off the waxy coating. Rinse thoroughly.
Marinate tongue in soy sauce, vinegar, brown sugar, onion, peppercorn and garlic for about 2 hours.
Drain then fry in hot oil until golden brown. Pour off excess oil leaving just 3 tablespoons of oil on the pot.
Put back on the pot the fried tongue, marinade liquid and enough water to cover. Simmer gently until tender.
Add tomato sauce, olives and bell pepper. Season to taste.
Cook until done.
To serve, slice tongue and top with sauce and garnish with fried bananas.