Wash the tomato, pat dry and cut each into 8 pieces.
In a medium bowl, mix together the ground pork with half of the chopped yellow onion, ½ heaping teaspoon of salt and ¼ teaspoon of black pepper.
Divide the pork mixture into 1 oz balls, about 16 to 17 meatballs.
Open the tofu package, drain and pat dry. Cut each tofu block into 8 slices. Cut each slice in half leaving about ¼” at one side such that it opens up like a book.
Flatten one meatball and stuff one slice of tofu with the meatball.
Repeat the process for all the tofu slices. If using two blocks of tofu, you may have just one meatball left over. If using just one block of tofu, you will have a mixture of stuffed tofu and meatballs.
Add frying oil to a frying pan with higher side to avoid too much splashing, heat over high heat.
When the oil is hot, fry the stuffed tofu for 3 minutes on each side until golden brown. Remove them to a plate lined with paper towel to absorb the excess oil when finished.
Fry the plain meatballs just until brown on each side if using, about 1 - 2 minutes. Remove them to a plate lined with paper towel to absorb the excess oil when finished.
Remove most of the oil, leaving just 1 tablespoon in the pan, add the rest of the chopped yellow onion and cook over medium heat until translucent.
Add the cut up tomato and cook until a sauce form but tomato pieces are not completely disintegrated. Season with salt and pepper, start with ½ teaspoon of salt and ¼ teaspoon of black pepper and adjust to taste.
Add the stuffed tofu and meatballs back into the sauce and let simmer for 10 minutes longer to allow the flavor to meld together.
Just before taking the pot off the heat, stir in a hand full of sliced green onion.
Reserve some green onion for garnish if desired.