1 1/2 cups quinoa, rinsed well
2 3/4 cups water
1/2 teaspoon kosher salt
2 cups cherry or grape tomatoes, halved
1 large English cucumber, chopped
2 small bell peppers, cored, seeded, and chopped
Kosher salt
Freshly ground black pepper
1 cup store-bought or homemade basil pesto
1 tablespoon red wine vinegar
Combine the quinoa, water, and salt in a medium saucepan and bring to a boil. Reduce the heat to low, cover, and simmer until the quinoa is tender and all the liquid is absorbed, about 15 minutes. Fluff with a fork and transfer the quinoa to a rimmed baking sheet, spread into an even layer, and refrigerate until cooled completely, 10 to 15 minutes.
Place the pesto and vinegar in a large bowl and stir to combine.
Add the cooled quinoa, cucumber, peppers, and tomatoes to the dressing and toss to combine and evenly coat. Taste and season with salt and pepper as needed. Serve at room temperature or chilled.
Make ahead: The salad can be made up to 1 day ahead and stored in the refrigerator.
Leftovers can be refrigerated in an airtight container for up to 3 days.