Pour couscous into a large salad bowl. Stir tomato paste and vegetable bouillon together in the cup you used to measure the couscous. Fill the measuring cup with boiling water and pour over couscous. Add another 1/2 cup of boiling water and stir. Cover bowl with a large plate and allow couscous to steam for 5 minutes. Fluff with a fork.

Add tomatoes, cucumber, bell pepper, green onions, parsley, and basil. Stir together olive oil, white balsamic vinegar, salt, and pepper in a cup. Pour over couscous salad and mix well.