Preheat your oven to 400°F (200°C). Line a baking sheet with parchment paper. Pat the tofu dry with paper towels to remove excess moisture. Cut into bite-sized cubes (about 1-inch pieces).
In a large bowl, toss the tofu cubes with cornstarch and oil until evenly coated.
Spread the tofu in a single layer on the prepared baking sheet. Bake for 20 minutes until the tofu is golden and crispy on the edges.
While the tofu bakes, whisk together the pineapple juice, soy sauce, sweet chili sauce, lime juice, crushed garlic, and grated ginger in a small bowl.
Remove the baking sheet from the oven. Add the chopped bell peppers, red onion, pineapple chunks, and jalapeños (if using) to the pan with the tofu. Pour the sauce evenly over everything and toss gently to coat.
Return to the oven and bake for an additional 40 minutes, stirring halfway through, until the vegetables are tender and caramelized and the sauce has thickened slightly.
Serve over rice and garnish with green onions and sesame seeds, if desired.
For meal prep, let cool completely before dividing into 4 airtight containers with rice.