Bring a large pot of salted water to a boil. Add the asparagus and cook for 2-3 minutes until bright green and tender-crisp. Drain and immediately transfer to a bowl of ice water to stop the cooking process. Let cool for 5 minutes, then drain again and pat dry.
In a large mixing bowl, combine the cooled asparagus, cherry tomatoes, red onion, and feta cheese.
In a small bowl, whisk together the olive oil, balsamic vinegar, Dijon mustard, salt, pepper, and garlic powder (if using) until well combined.
Pour the dressing over the salad and toss gently to coat all the ingredients evenly.
Serve immediately or refrigerate for up to 30 minutes to allow the flavors to meld.