Bring a large pot of salted water to a rolling boil. Add 1 lb of your favorite pasta and cook according to package instructions until al dente, typically around 8-10 minutes. Reserve 1 cup of the pasta water, then drain the pasta and set it aside.

In a large skillet, heat 4 teaspoons of olive oil over medium heat. Add the diced onion and sauté for 1 minute until fragrant. Then, introduce 7 cups of sliced yellow squash, 4 minced garlic cloves, 1 1/4 teaspoons of salt, 3/4 teaspoons of black pepper, and 1/4 teaspoon of crushed red pepper flakes. Cook for 15-20 minutes until the squash is tender and lightly browned.

Carefully transfer the cooked squash and onion mixture to a blender. Puree on high until smooth. If you prefer a chunkier sauce, pulse gently for a few seconds.

Return the blended sauce to the skillet over low heat. Gradually stir in 1 1/4 cups of grated Parmesan cheese until it melts. Toss in the drained pasta and mix thoroughly, adjusting the sauce’s consistency with reserved pasta water.

Stir in 1 tablespoon of lemon juice and taste to adjust seasonings. Fold in 1/4 cup of chopped fresh parsley just prior to serving.