Heat 8 cups broth to a simmer, turn the heat down and keep hot on the stove.

In medium sized heavy pot heat the olive oil over medium heat.

Add in the onions and cook until softened, 2-3 minutes.

Add the rice, stir, and cook another 2-3 minutes.

Add the vermouth and cook until it’s mostly absorbed, about 2 minutes.

Start to ladle in the broth about a cup at a time, letting each addition cook until mostly absorbed, stirring often.

Repeat until rice is cooked to al dente (you may not need all the broth).

Stir in the lemon zest, lemon juice, parmesan and butter. Stir well until all is incorporated.

Season well with salt and pepper.