How can I get my pasta dish to be more cohesive?

I make this dish where I sautee zucchini, onions and garlic in EVOO, add salt and pepper to taste, add cooked pasta and top with cheese. It's really delicious and simple but I feel like the dish isn't really cohesive. I feel like the cheese doesn't stick to the pasta or zucchini, it just slides right off. The dish becomes almost watery, like everything is all together but there's nothing making it a dish, holding it together. I have tried using er only, and EVOO and er. My other problem is that I add the garlic and onions to the oil first, cook a minute before adding the zucchini. But by the time the zucchini is done cooking the onions and garlic are burned. I have tried adding the onions and garlic later on which works well, but I always heard that it's good to add the aromatics to the oil first so it infuses the flavor. Same thing happened when I made hash browns the other night too, burned onions by the time the potatoes were done. Does anyone have any suggestions to my cooking woes?