Fill a medium pot with water and add a generous pinch of salt. Bring it to a rolling boil over high heat, then add the tagliatelle pasta. Cook according to package instructions, usually around 8-10 minutes, until al dente. Reserve about half a cup of the pasta water, then drain the pasta in a colander.

While the pasta cooks, heat 2 tablespoons of olive oil in a large skillet over medium heat. Add the minced garlic and sliced onions, sautéing for about 3-4 minutes until the onions turn translucent and fragrant.

Stir in the sliced baby Bella mushrooms and zucchini to the skillet, cooking for about 5 minutes until the mushrooms soften and the zucchini becomes tender.

Once the vegetables are tender, sprinkle in red pepper flakes, salt, and black pepper to taste. Stir in the pesto sauce, mixing thoroughly until the vegetables are evenly coated.

Carefully add the drained tagliatelle pasta directly into the skillet with the sautéed vegetables. Toss everything together gently, adding reserved pasta water a little at a time to achieve your desired sauce consistency.

Plate the Zucchini Mushroom Pasta immediately, garnishing with freshly chopped parsley and grated parmesan cheese if desired.