Step 1Slice the tomatoes in half lengthwise and place them in a medium mixing bowl. Add the salt, garlic, jalapeño, olive oil, lemon juice and green onions, and stir to combine. Set aside to let the salt draw out the tomato juices.
Step 2Toast the couscous in a dry medium saucepan over medium-high heat and cook, stirring frequently, until it smells nutty, 3 to 5 minutes. Add 3 cups water and 1 teaspoon salt, and bring to a boil. Reduce heat and cook, partially covered, until the couscous is just tender but still a little chewy, 5 to 7 minutes. Drain, rinse under cool running water and shake well to remove as much moisture as possible.
Step 3While the couscous is still slightly warm, add it to the tomato mixture and toss to coat. Set aside to cool completely.
Step 4Add the cucumbers, feta, mint and parsley just before serving, and stir gently to combine. Add black pepper to taste and stir that in. Taste again and add more salt or lemon juice if your think it's necessary.