Cook the tortellini according to the package directions.
Meanwhile, heat the oil in a large skillet over medium heat. Add the onion and cook until soft, about 6 minutes. Increase heat to medium-high. Add the butter and cook until it turns golden brown, about 3 minutes. Stir in the garlic, peas, 1/2 teaspoon salt, and 1/4 teaspoon pepper and cook until heated through, 2 to 3 minutes. Add the tortellini, tarragon, and half the Parmesan and toss.
Divide among bowls and sprinkle with the remaining Parmesan.
This was so easy and my whole family devoured it. Even my 2 and 5 year old! The
Previous reviewers recommendation to add mushrooms is a good one. I may try that next time. I served with some cheese bread.