Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper.
Press the tofu block between paper towels for 15 minutes to remove excess moisture, then slice into 1-inch uniform cubes.
In a medium bowl, toss the tofu cubes with cornstarch, sea salt, and black pepper until each piece is evenly coated.
Arrange the tofu in a single layer on the baking sheet and bake for 25 to 30 minutes, flipping halfway through, until the edges are golden and crispy.
While the tofu bakes, whisk together the peanut butter, tamari, rice vinegar, sriracha, grated ginger, and minced garlic in a small bowl until smooth.
Steam the broccoli florets and sliced red bell pepper in a steamer basket over boiling water for 4 to 5 minutes until tender-crisp.
Transfer the crispy tofu and steamed vegetables to a large bowl, drizzle with the peanut sauce, and toss gently to coat before serving.