In a medium-sized pot, bring 2 cups of water or vegetable broth to a boil. Add the rinsed quinoa, reduce the heat to low, cover, and simmer for about 15 minutes, or until the water is absorbed. Remove from heat and let it sit for 5 minutes, then fluff with a fork.
While the quinoa is cooking, prepare the dressing by whisking together lime juice, olive oil, salt, pepper, and cumin (if using) in a small bowl. Set aside.
In a large mixing bowl, combine the cooked quinoa, diced avocado, cherry tomatoes, cucumber, red onion, and cilantro.
Drizzle the dressing over the salad and gently toss to combine, ensuring the avocado remains intact.
Taste and adjust seasoning if necessary, adding more lime juice, salt, or pepper as desired.
Serve immediately, or refrigerate for 30 minutes to allow the flavors to meld together.