Mashed Potato Salad With Scallions and Herbs

red potatoes, cut into 1 1/2-inch chunks

Finely grated zest and juice of 1 lemon, plus more lemon juice for serving

minced fresh rosemary

fine sea salt, more as needed

coarsely ground black pepper

or two of hot sauce, to taste

extra-virgin olive oil, more for drizzling

mayonnaise, sour cream or crème fraîche

Dijon or whole-grain mustard

thinly sliced scallions (white and green parts)

chopped parsley

chopped basil or dill