Cook the pasta: Bring a large pot of salted water to a boil. Cook the pasta according to package directions until al dente.
Drain and rinse briefly under cool water to stop the cooking. Shake off excess water.
Prep the cucumber: If grating, sprinkle with a pinch of salt and let it sit for 5 minutes. Squeeze out excess moisture with clean hands or a kitchen towel.
This keeps the sauce from getting watery.
Make the avocado tzatziki: In a large bowl, mash the avocado until mostly smooth. Stir in Greek yogurt, garlic, lemon juice, lemon zest, olive oil, dill, and mint. Season with salt and pepper.
Taste and adjust lemon or salt as needed.
Fold in the veg: Add the cucumber, red onion, and cherry tomatoes. Stir gently to combine.
Toss with pasta: Add the cooled pasta to the bowl. Toss until the pasta is evenly coated and the veggies are distributed.
If the sauce feels thick, add a splash of water or olive oil to loosen it.
Top and rest: Sprinkle with crumbled feta if using. Let the salad sit for 10–15 minutes to let the flavors mingle. Serve chilled or at cool room temperature.