Bring a large pot of salted water to a boil and cook the capellini until al dente. Since capellini cooks very quickly, keep an eye on it to avoid overcooking. Reserve a little pasta water before draining.
Heat a tablespoon of olive oil in a pan and add the breadcrumbs. Stir continuously until they turn golden and crispy. Remove them from heat and set aside to maintain their crunch.
In the same pan, add olive oil and sauté garlic until fragrant. Toss in the chopped green olives and chili flakes, letting them cook briefly to release their flavors. The aroma at this stage is incredible.
Add the cooked capellini to the olive mixture along with a splash of reserved pasta water. Toss everything gently so the pasta absorbs the sauce evenly. The starch in the water helps bind the flavors together.
Turn off the heat and add lemon zest, parsley, and black pepper. Sprinkle toasted breadcrumbs on top and finish with grated parmesan if desired. Serve immediately while warm.