Bring a large pot of lightly salted water to a boil. Cook tortellini according to package instructions. Drain well. Reserve cooking pot.
Meanwhile, heat olive oil in a large cast iron skillet over medium high heat. Add onion and salt and cook, stirring often until the onion starts to soften and become translucent, 3 to 5 minutes. Add summer squash and cook, stirring often until starting to soften slightly, 1 to 2 minutes. Add in green beans and continue cooking, stirring often until the vegetables are crisp-tender.
Return the tortellini to the pot, and gently stir in the vegetables, pesto, basil and pepper. Stir to coat. Serve hot.
