Finely dice the red onion into ¼-inch pieces and place in a bowl with the lemon juice, lemon zest, and 1.25 tsp salt—this quick pickling will soften the onion's bite and add brightness to the salad. Mince the garlic cloves and parsley, coarsely chop the pistachios, and roughly chop the mint and arugula. Having all your fresh components prepped and ready allows you to work quickly once the couscous is done, ensuring the salad comes together efficiently while everything is at its best.

Bring 1.75 cups water to a boil in a pot with 1 tsp salt, then add the 1.25 cups pearl couscous. Return to a boil, then reduce heat to low and simmer uncovered for 8-10 minutes until the water is completely absorbed. While the couscous cooks, blanch the peas in a separate pot of boiling salted water for just 1½ minutes, then drain and set aside—this brief cooking keeps them bright green and tender-crisp. When the couscous is done, remove from heat, cover, and let sit for 5 minutes to allow the grains to finish absorbing any remaining moisture.

While the couscous rests, warm 4 tbsp olive oil in a small pan over medium heat. Add the minced garlic and cook for 2-3 minutes, stirring frequently, until the garlic turns golden and fragrant—be careful not to let it brown too much or it will become bitter. Once golden, immediately stir in the za'atar, cumin, 1 tsp salt, and red pepper chili flakes, cooking for just 30 seconds to bloom the spices. Remove from heat and set aside—I prefer using a robust olive oil here because its peppery finish complements the warm spice blend beautifully.

Fluff the rested couscous with a fork to separate the grains, breaking up any clumps gently. Transfer the couscous to a large mixing bowl and add the blanched peas from Step 2. Pour in the pickled red onion mixture from Step 1 (including all the liquid), then add the chopped arugula, fresh parsley, mint, and pistachios. Toss everything together gently but thoroughly to combine, ensuring the flavors distribute evenly throughout the salad.

Pour the warm garlic-spiced oil mixture from Step 3 over the assembled salad and toss well, making sure every component is coated with the fragrant oil and spices. Taste the salad and adjust seasoning as needed, adding sumac to taste for an extra pop of bright, tangy flavor. Serve immediately while the oil is still warm and the vegetables are fresh and crisp, or let it cool to room temperature—both versions are delicious, though I find serving it slightly warm allows the spices to really shine.