Put the corn husks in a roasting pan of warm water; soak until softened, about 30 minutes.
Meanwhile, prepare the dough: Whisk the masa harina, baking soda and sea salt in a large bowl. Stir in the chicken broth and lard with a wooden spoon to make a thick dough. (If it seems dry, add a splash of broth.) Let the dough rest 30 minutes. Meanwhile, preheat the broiler. Put the poblanos on a foil-lined broiler pan; broil, turning, until charred, about 7 minutes. Transfer to a bowl, cover with plastic wrap and set aside 10 minutes. Peel off the skins, then stem, seed and dice the peppers.
Heat the butter and vegetable oil in a skillet over medium heat. Add the onion and scallions and cook until soft, about 5 minutes. Add the poblanos, tomatoes and vinegar, season with kosher salt and pepper, and cook 5 more minutes. Remove from the heat and let cool completely. Fold in both cheeses.
Remove the corn husks from the water and gently squeeze dry. Tear 4 husks into thin strips to use as ties. Spread a heaping tablespoonful of dough onto the wide end of each remaining husk, leaving a 1/2-inch border on the top and both sides and 3 inches on the tapered end. Spread 1 tablespoon of the cheese mixture over the dough, then roll up the tamale into a cigar shape. Fold up the tapered end and tie closed with a strip of husk.
Put the tamales upright in a steamer basket set over a few inches of boiling water; steam until the filling is firm, 30 to 40 minutes. Remove the tamales and let rest 10 minutes.
Mix the sour cream and lime zest in a small bowl and season with kosher salt. Unwrap the tamales and serve with the lime sour cream.