Pat the tofu dry with paper towels to ensure a crisp sear, then season with salt and pepper.

Heat a portion of the oil in a large Dutch oven over medium-high heat until it shimmers. Add the tofu and cook, turning occasionally, until golden brown on all sides, 5 to 7 minutes; transfer to a plate and set aside.

Add the remaining oil to the pot and stir in the squash and eggplant. Cook, stirring occasionally, until the vegetables are browned in spots and beginning to soften, about 10 minutes.

Stir in the onion and cook until translucent and softened, about 5 minutes. Add the garlic, ginger, and bruised lemongrass and cook until fragrant.

Pour in the coconut milk and broth, then return the tofu to the pot. Bring the liquid to a simmer, then reduce the heat to medium-low, cover, and cook until the squash is tender throughout, about 20 minutes.

Remove and discard the lemongrass stalk. Stir in the cilantro, lime juice, and soy sauce, then adjust seasoning with salt and pepper. Serve hot with rice, topped with the scallions.