Step 1
Cook 12 oz. medium pasta (such as gemelli or fusilli) in a large pot of boiling salted water, stirring occasionally, until al dente. Drain and rinse under cold running water to remove excess starch. Step 2
Meanwhile, heat ½ cup extra-virgin olive oil in a skillet over medium-high. Add 3 Tbsp. pine nuts and 2 Tbsp. drained capers; cook, stirring often, until nuts are golden brown and capers are crisp, about 3 minutes. Using a slotted spoon, transfer fried nuts and capers to paper towels and let drain. Step 3
Add 1 large onion, thinly sliced, and 4 garlic cloves, finely chopped, to same pan and season with 1 tsp. Diamond Crystal or ½ tsp. Morton kosher salt. Stir to combine, then cook, stirring often, until onion starts to soften and garlic is fragrant, about 3 minutes. Add 2 Tbsp. double-concentrated tomato paste and ½ tsp. crushed red pepper flakes and cook, stirring occasionally, until tomato paste is slightly darkened in color, about 4 minutes. Transfer onion mixture to a large bowl and let cool 5–10 minutes. Step 4
Add pasta, 1 bunch parsley, leaves and tender stems coarsely chopped, ½ cup Castelvetrano olives, pitted, smashed, halved, ½ cup chopped oil-packed sun-dried tomatoes, 2–3 tsp. finely grated lemon zest, 3 Tbsp. fresh lemon juice, and remaining 2 Tbsp. drained capers to onion mixture and toss to combine. Taste and add more lemon juice and season with more salt if needed. Step 5
To serve, top pasta salad with fried pine nuts and capers. Sprinkle with more red pepper flakes and drizzle with oil.
Do ahead: Pasta can be cooked 3 days ahead; transfer to an airtight container and chill. Pine nuts and capers can be fried 1 day ahead; store airtight at room temperature separately. Salad (without toppings) can be assembled 8 hours ahead; cover and chill.