In a medium bowl, whisk together corn masa harina, baking powder, and kosher salt. In a stand mixer fitted with the paddle attachment, beat the lard on medium to medium-high speed until smooth and fluffy, 3–5 minutes.
Scrape down the sides and bottom of the bowl. Add the masa mixture to the lard in three portions, adding a little warm broth with each addition to help the masa come together.
While the mixer is running, gradually pour in more broth along the side of the bowl with each portion, helping the masa stay loose and come together into a smooth, spreadable dough.
Once all the masa has been added, slowly pour in the remaining broth in a steady stream, mixing continuously until the dough is soft, smooth, and spreadable—similar to thick hummus.
The exact amount of broth may vary depending on its temperature and the brand of masa, so stop once the dough reaches the right consistency. You’ll need about 4–5 cups in total.
Once the dough is ready, mix for 5 minutes on medium speed until fully combined.
Place a large baking dish half-filled with water on the bottom rack of your oven, close the door, and preheat to 400°F.