1. Adjust oven rack to center position and preheat oven to 375°F. Press tofu firmly between paper towels to remove excess moisture. Cut into 1 1/2–inch cubes and set aside.
2. In a medium bowl, whisk together miso paste, 2 tablespoons lemon juice, lemon zest, and 1 tablespoon oil. Season generously with salt and pepper. Add tofu and toss to coat.
3. Spread tofu evenly over a foil-lined rimmed baking sheet. Place in oven and bake until golden brown, about 20 minutes. Sauce may darken a little against the foil; this is fine. Set tofu aside.
4. Combine nut milk and cauliflower in a small saucepan. Season with salt and bring to a simmer. Cook until cauliflower is tender, about 10 minutes. Purée mixture using a hand blender or countertop blender. Set aside.
5. Heat remaining 2 tablespoons vegetable oil in a large saucepan or saucier over medium heat until shimmering. Add garlic, ginger, and chilies and cook, stirring, until fragrant and lightly browned, about 1 minute. Add coriander, cumin, and turmeric and cook, stirring, until fragrant, about 30 seconds. Add spinach and arugula one handful at a time, stirring and adding more as the greens wilt (see note).
6. Reduce heat to low and cook, stirring occasionally, until greens are fully wilted, about 5 minutes. Stir in cauliflower purée and continue to cook until greens are very tender, about 5 minutes longer. Stir in tofu cubes and heat through. Stir in remaining lemon juice, season with salt, adjust consistency with a little water if necessary, and serve.