Press tofu for 10 minutes to remove excess moisture.
Coat tofu in cornstarch for that perfect crisp.
Heat vegetable oil in wok over medium-high heat.
Add tofu cubes and fry until golden brown, about 6 minutes.
Remove tofu and set aside.
In the same wok, add sesame oil, garlic, and ginger; stir 30 seconds.
Add onions, bell peppers, and pineapple; stir-fry 3 minutes.
In a bowl, whisk soy sauce, vinegar, tomato paste, maple syrup, and chili sauce.
Pour sauce into wok and simmer until slightly thickened.
Add tofu back, toss until evenly coated, and serve immediately with rice or noodles.