Preheat the oven to 425°F and line two large baking sheets with parchment paper.

Whisk the cornstarch, oil, and soy sauce together in a large bowl. Add the tofu cubes and toss gently with a spatula until coated, then spread onto one baking sheet in an even layer so the pieces are not touching.

Place the cauliflower florets on the second baking sheet. Drizzle with oil, sprinkle with salt, and massage the oil into the florets until coated before spreading them into a single layer.

Place the tofu on the middle rack and the cauliflower on the top rack. Bake for 20 minutes, then flip the pieces and continue roasting for another 20 minutes until the cauliflower is tender and charred and the tofu is firm and crisp.

Combine the soy sauce, maple syrup, tomato paste, vinegar, sriracha, cornstarch, pepper, and water in a small bowl while the vegetables roast, whisking until the cornstarch is fully dissolved.

Heat the oil in a large wok or sauté pan over medium-high heat until it shimmers. Add the ginger, garlic, white parts of the scallions, and red chilies, cooking until they are lightly browned and smell fragrant.

Pour in the whisked sauce mixture and simmer until it begins to bubble and thicken slightly.

Fold in the roasted tofu and cauliflower and stir to coat thoroughly. Simmer until the sauce thickens into a glossy glaze that clings to the vegetables.

Garnish with the green parts of the scallions and serve hot while the textures are still crisp.