Lemon and Green Pea Risotto

Ingredients

• quart low-sodium chicken broth OR vegetable broth
• tablespoons salted butter, cut into 1-tablespoon pieces, divided
• small yellow onion, finely chopped
• Kosher salt and ground black pepper
• Arborio rice
• frozen peas, thawed and patted dry
• teaspoons grated lemon zest, plus 2 tablespoons lemon juice
• ounce Parmesan cheese, finely grated , plus more to serve
• Finely chopped fresh flat-leaf parsley OR basil OR mint, to serve