A combination of shortcut ingredients and techniques makes this meal ready in about 20 minutes. Microwaving the potatoes instead of boiling keeps them from getting waterlogged and primes them to absorb the pesto. Combining potatoes, pesto and pasta is a classic Italian combination, and turns the panty staples used in this recipe into a hearty meal.
Bring a large pot of salted water to a boil. Add the pasta and cook as the label directs; add the beans during the last 2 minutes of cooking. Reserve 3/4 cup cooking water, then drain. Set the pot aside.
Meanwhile, pierce the potatoes all over with a fork. Microwave until tender, about 5 minutes. Let cool slightly, then chop.
Heat the olive oil in the reserved pot over medium-high heat. Add the potatoes, season with salt and pepper and cook, stirring occasionally, until lightly browned, about 5 minutes. Add the pasta and green beans and stir to coat. Remove from the heat and add the pesto, lemon zest and 1/4 cup reserved cooking water; toss to coat, adding more cooking water as needed to loosen. Season with salt and pepper.