Roughly dice the tofu and marinate in the soy sauce. Turn it every now and then.
Mix flour, cornstarch, baking powder, salt and water into a relatively viscous dough and allow to sit.
In the meantime, prepare the other ingredients: clean or peel the carrots and cut into thin strips. Cut the bell pepper, pineapple and onion into bite-sized pieces. Finely chop the garlic.
Mix the ketchup, soy sauce, rice vinegar, sugar, cornstarch, pineapple juice and water to a smooth sauce. Add the pineapple pieces.
Flour the tofu cubes well on all sides, then pull them through the batter and deep-fry them in a saucepan with hot oil for a few minutes until golden brown. Remove and drain on some paper towel or a cloth.
Heat a pan with a dash of vegetable oil over medium to high temperature. Fry the garlic, onion, bell pepper and carrot for about 1 minute. Then add the sauce, bring to the boil briefly and simmer for another 1-2 minutes. Fold in the deep-fried tofu. Serve with rice.