In a small bowl or pint-sized jar, combine the vinegar, sugar, and salt. Microwave for 45 to 60 seconds, or until the mixture is hot. Stir until the sugar and salt fully dissolve. Add the sliced red onion, pressing down to submerge it completely in the liquid. Cover and let it rest for at least 30 minutes to pickle, allowing the onions to soften and absorb the tangy flavor.

In a medium saucepan, combine the quinoa with 2 cups of water and the salt. Bring to a boil over high heat, then reduce the heat to low, cover, and simmer for 15 to 18 minutes until the water is absorbed and the quinoa is tender. Remove from heat and fluff the grains gently with a fork. Let it cool slightly before adding to the salad.

In a small jar or bowl, combine the olive oil, lemon juice, honey, salt, and pepper. If using a jar, secure the lid and shake vigorously until the dressing becomes emulsified and creamy. If using a bowl, whisk until smooth and well combined. Taste and adjust seasoning with extra salt or pepper if desired. Set aside.

In a large mixing bowl, combine the cooked quinoa, halved tomatoes, diced cucumber, feta cheese, olives, sliced basil, and drained pickled onions. Pour in about ¼ cup of the lemon dressing and toss gently until everything is well coated. Taste the mixture and add more dressing, salt, or pepper as needed to balance the flavors.

Finally, add the arugula and fold it through just before serving to keep the leaves crisp and fresh. Serve immediately, garnished with extra basil or feta if desired.

This vibrant salad is a refreshing balance of tangy, sweet, and savory — perfect as a light main dish or a colorful side for any meal.