Heat a large heavy-bottomed pan over medium heat. Add the olive oil, then the diced onion. Season with salt and red pepper flakes and sauté until the onion becomes translucent and fragrant, about 5 minutes.

Add the dry pasta directly to the pan and cook for about 5 minutes, stirring often, until lightly toasted. Stir in the peas and cook until they’re warmed through and bright green.

Pour in the lemon juice, lemon zest, black pepper, and vegetable broth. Simmer uncovered for about 15 minutes, stirring occasionally, until the pasta is al dente and most of the liquid has been absorbed. Add a splash of water if the pan becomes too dry (the starch from the pasta should create a light, creamy sauce that coats the noodles and peas).

Finish with shaved Parmesan cheese and an extra extra black pepper if desired. Serve immediately.