Bring a large pot of water to a boil. Rinse the cornhusks under cold water, place them in a heatproof bowl, and cover them with the boiling water. Place a heatproof plate on top of the corn husks and weight the plate down with a large can to keep the husks submerged. Let the husks sit until soft, at least 30 minutes.

Meanwhile, in a large bowl, combine the butter, shortening, and sugar. Using your hands or a mixer with the paddle attachment, mix together until very creamy. Add the masa harina and mix well—the texture should resemble a coarse meal.

In a small bowl, mix together a few drops of the food coloring (if using) with 3 tablespoons of the milk, then gradually add to the masa harina mixture, along with the remaining milk, until fully combined. Stir in the lime zest and salt.

Once softened, drain the corn husks. Working one at a time, scoop about ¼ cup of the batter into 1 husk, using a spoon to spread the batter into a rectangle. Leave at least a 1-inch border all around the batter, and a little more on the longer sides. If the husks are too small or broken, place two together, overlapping them.

Fold one of the long sides of the corn husk toward the center, then fold the other long side on top and tuck the sides underneath. If the husks are still too small to wrap the batter, wrap the tamale in another husk and tie it with a thin strip of husk to hold the batter in place during cooking (you don’t need to do this—it’s just an extra precaution).

Repeat with the remaining husks and batter until all of the batter is used.

Place the assembled tamales in a tamale steamer and cover. Steam the tamales until the masa is fully cooked.

Let the tamales cool slightly before serving.