STEP 1: Bring a large pot of water to a boil. Cook pasta until just tender, 4 to 5 minutes or according to package directions.
STEP 2: Meanwhile, place 1 tablespoon oil and garlic in a large skillet. Cook over medium heat, stirring occasionally, until the garlic is sizzling and fragrant, 2 to 5 minutes. Add sweet potato, bell pepper, tomatoes and water and cook, stirring occasionally, until the bell pepper is tender-crisp, 5 to 7 minutes. Remove from the heat; cover and keep warm.
STEP 3: Drain the pasta, reserving 1/2 cup of the cooking water. Return the pasta to the pot. Add the vegetable mixture, the remaining 1 tablespoon oil, parsley, tarragon, vinegar (or lemon juice), salt and cheese; toss to combine. Add the reserved pasta water, 2 tablespoons at a time, to achieve the desired consistency.