Place the dried anchos in a heatproof bowl and cover with 2 cups of boiling water. Let them soak for about 15 minutes until very soft, then drain the chilies and discard the soaking liquid.

Combine the softened anchos, onion, 1/4 cup water, tomato paste, garlic, cumin, sugar, and salt in a blender. Process until the mixture forms a thick, smooth puree, about 1 minute, stopping to scrape down the sides of the blender jar as needed.

Melt one tablespoon of butter in a 12-inch skillet over medium heat. Add the ancho puree and cook, stirring frequently, until the mixture smells fragrant and thickens slightly, about 3 minutes.

Whisk in the 1 3/4 cups water until the sauce is smooth.

Lay the tofu in the skillet in an even layer and bring the liquid to a simmer. Reduce the heat to low and simmer gently for about 30 minutes, allowing the tofu to warm through and the flavors to meld.

Carefully transfer the tofu to a serving platter. Stir the remaining two tablespoons of butter and the lime juice into the sauce, then season with salt and pepper to taste.

Pour the sauce over the tofu, sprinkle with cilantro, and serve hot with lime wedges.