Bring a large pot of salted water to a boil. Cook the pasta until al dente and reserve 3/4 cup pasta cooking water. Drain the pasta and set aside.

Add the walnuts to a large skillet and turn the heat to medium. Cook, turning often, for 1-2 minutes or until the walnuts are well toasted. Transfer the walnuts to a mortar and pestle, food processor, or zip lock bag and mash or pulse until finely chopped.

In a bowl, combine the walnuts, lemon zest, minced parsley, and parmesan cheese. Season with salt and pepper.

In the same pan used to toast the walnuts, heat the neutral cooking oil over medium heat. Add the diced onion and cook for 6-7 minutes until translucent and softened.

Add the butter to the pan. Once it is melted and frothy, add the tomatoes and turn the heat to medium-high. Cook without moving for 4-6 minutes, adjusting the heat if necessary, until the tomatoes begin to char and soften. Season with salt, pepper, and crushed red pepper.

Pour the reserved pasta cooking water into the pan and scrape up any browned bits stuck to the bottom. Bring to a low boil and keep the liquid at a slow and steady boil for 4-5 minutes until the broth is reduced and thickened.

Stir in the torn basil leaves and the lemon juice. Taste and season the sauce to your preferences and reduce heat to low.

Add the pasta to the pan and toss to coat with the sauce. Once the pasta is glossy and well-coated, turn off the heat.

Divide the cooked tomato-basil pasta between shallow pasta bowls and pile the walnut gremolata on top. Enjoy!