Place a large pot over medium-low heat. Add the olive oil and diced onion and cook, stirring occasionally, until the onion is soft and translucent, about 5–7 minutes. Stir in the crushed red pepper and cook briefly, about 30 seconds.

Pour in the water, add the sea salt, and stir in the frozen peas. Bring the mixture up to a boil, then use a wooden spoon to press and mash some of the peas against the side of the pot to create a slightly creamy base.

Add the ditalini to the pot, reduce heat to maintain a gentle simmer, and cook until the pasta is al dente. Stir frequently to prevent sticking and add more hot water if the pot starts to dry out so the dish stays saucy.

When the pasta reaches the desired tenderness, remove the pot from the heat and fold in most of the grated Pecorino Romano until it melts into the sauce. Taste and adjust seasoning with additional salt and freshly ground pepper. If the mixture seems dry, stir in a splash of hot water to loosen it.

Ladle the pasta into bowls, finish each serving with a drizzle of extra virgin olive oil and a generous sprinkle of Pecorino. Serve immediately.