1. In a large shallow bowl, add the tofu cubes and soy sauce, and gently toss to coat. Then add the cornstarch, salt, and pepper. Stir gently until all the pieces are well coated.
2. Heat a large skillet over medium-high heat and add the oil. Once hot, add the tofu and cook for 7 to 10 minutes, or until crispy and golden on all sides. Avoid stirring the tofu too much during cooking, as it may crumble. Only stir it every two minutes.
3. While the tofu is cooking, prepare the sauce: whisk together the sauce ingredients in a small bowl.
4. If you choose to enjoy this stir-fry with rice, it is now time to start cooking it according to the instructions on the packaging.
5. Once the tofu is golden, transfer it to a bowl and set it aside.
6. Place the same large skillet back on the heat, add the oil, onion, and carrot. Cook for 4 to 5 minutes.
7. Then add the bell peppers and pineapple chunks and cook for another minute.
8. Add the sweet and sour sauce to the vegetables in the skillet, along with the tofu. Simmer for 3 minutes, or until the sauce thickens slightly.
9. Remove from heat, serve with rice, garnish, and enjoy!