In a large pot, melt the butter over medium heat. Add the bell pepper, scallion whites and garlic; cook until fragrant, about 1 minute. Add the curry paste and cook, stirring constantly, until fragrant, about 1 minute.
Stir in the zucchini, carrot, coconut milk, vegetable stock, protein powder, peanut butter, stevia, salt and black pepper. Bring to a boil, then reduce the heat to medium-low and simmer uncovered until the vegetables are tender, 8 to 10 minutes. Taste and adjust the seasoning if necessary.
Add the tofu and simmer for 5 minutes to warm through. Add the spinach and cilantro to wilt. Taste and adjust the seasoning if necessary.
Divide the curry among four bowls. Drizzle 1 tablespoon melted coconut oil over each portion. Sprinkle with the scallion greens and more cilantro.
