Rinse quinoa under cold water until water runs clear. In a medium saucepan, bring quinoa and water or stock to a boil.
Reduce heat to low, cover, and simmer for 15-18 minutes until quinoa is tender and liquid is absorbed.
While quinoa cooks, heat oil in a large skillet over medium heat. Add chopped onion and cook for 5-6 minutes until softened and lightly browned.
Add minced garlic to the skillet and cook for another 30 seconds until fragrant.
Fluff cooked quinoa with a fork and add to the skillet with sautéed onion and garlic.
Stir in drained black beans and ground cumin. Cook for 2-3 minutes until heated through.
Season with salt, pepper, and lime juice to taste.
Remove from heat and garnish with fresh chopped cilantro before serving.