Preheat oven to 500°. Whisk flour, baking powder, salt, baking soda, and sugar together in a large bowl.
Add lard and rub into flour mixture with your fingertips, or use two knives to cut it in, until flour looks like fine meal with some pea-size lumps.
Make a well in flour mixture and pour in 1 cup buttermilk. Blend flour into buttermilk with your fingers. Mixture should be quite moist; add a little more buttermilk if you need to (with lard, it's likely).
Spread half the cornmeal on a work surface and turn biscuit dough onto cornmeal. Sprinkle with rest of cornmeal and pat into a 10-in. round, pressing in the cornmeal. Grease a large cast-iron skillet.*
Cut dough into 12 wedges. Using a spatula, transfer wedges to pan, spaced slightly apart so edges get crisp. Top each biscuit with a dab of butter.
Bake until golden, 20 to 25 minutes.
*Order fresh lard from your butcher, or buy at a farmers' market. You can also bake biscuits on a baking sheet, spaced a little apart, if you like.
Make ahead: Through step 5, 2 hours.