Put a couple layers of paper towel on a cutting board, place the tofu on top, add a couple more layers of paper towel on top, place another cutting board on top and add something heavy such as a couple of soup cans. Let sit for 15 minutes to extract moisture. Pat dry. Cut tofu into 16 equal sized pieces.
Pour 2 inches of oil into a heavy pot and heat to 350 degrees. Have a paper towel lined plate nearby.
Combine the flour, salt, and pepper. Add the sparkling stir well. Dip the tofu into the tempura batter and carefully lower into the hot oil. Fry for 3-4 minutes or until golden brown and crispy. Remove with a slotted spoon to the paper towel lined plate.
Put ponzu sauce in a serving bowl, add a few pieces of the green onion and the sesame seeds. Garnish the tofu with the rest of the green onion and serve.