Heat the olive oil and butter in a large skillet over medium heat. Once butter has melted, add in the onion and cook until soft, about 5 minutes.
Add in the zucchini and a big pinch of salt, cook for 20 minutes, stirring every 2-3 minutes.
While zucchini cooks, bring a large pot of salted water to a boil. Add in the pasta and cook according to package instructions. Reserve ½ cup of pasta water and drain pasta from remaining water.
Once zucchini is very soft and caramelized, add in the garlic and garlic powder. Cook for 2-3 minutes, or until garlic is fragrant.
Add the cooked pasta and ¼ cup of the reserved pasta water to the skillet with the zucchini. Stir everything together, and add more pasta water if pasta seems dry. Serve warm with fresh cracked black pepper.