Heat 1 tablespoon oil in a wide pot over medium-low heat. Add the onion and cook, stirring often for 5-6 minutes until it begins to turn translucent. Add the red Fresno chili pepper and cook for an additional 2-3 minutes.

Turn the heat to low and allow the onions to simmer in the oil as you finish the pasta and the pesto. Stir the onions occasionally to prevent them from burning.

Combine the pistachios, pine nuts, and garlic in a food processor and pulse until finely minced.

Add the arugula in batches and continue pulsing until all of the arugula is minced.

Slowly pour in the extra virgin olive oil and pulse until smooth. Add the basil leaves and continue pulsing until everything is incorporated and finely minced. Add more extra virgin olive oil, if needed. Season to taste with salt and pepper and set aside.

Bring a large pot of salted water to a boil and add the pasta. Cook until al dente. Reserve 1 cup of the pasta cooking water and set it aside. Drain the pasta and wipe out the pot.

Immediately return the pot to the stovetop and add the remaining 1 tablespoon neutral oil. Turn the heat to medium and add the tomatoes. Allow them to sizzle in the oil for 5-6 minutes as you finish the rest of the recipe. Once the skins are split, turn off the heat and season with salt and pepper.

Turn the heat on the aromatics to medium-high. Add half the pasta cooking water and bring it to a boil. Allow it to reduce and thicken for 2-3 minutes. Add the cooked pasta and turn the heat to low, and toss to coat.

Immediately add the pesto and continue tossing gently to coat the pasta with the pesto. Add more pasta cooking water, as needed, to loosen up the sauce—taste and season to your preferences. Turn off the heat.