Step 1

In a food processor, combine spinach, beans, garlic, salt, lemon juice, chili flakes, and vinegar. Blend until finely chopped. While the food processor is still running, pour in olive oil in a steady stream until pesto is blended and smooth. Taste and season with more salt and pepper as desired.

Step 2

Boil pasta in a pot of heavily salted water until al dente, according to package instructions. Drain, reserving 1 cup of hot pasta water. Thoroughly fold pesto in with the hot pasta. If the sauce is too thick, add in pasta water, 1 tablespoon at a time, until desired consistency. Top with Parmesan cheese and more chili flakes as desired and serve warm.