Bring a large pot of salted water to a boil. Add the spaghetti and cook according to package instructions until al dente.

While the pasta cooks, heat the oil or butter in a large pan or pot over medium heat.

If using, add the chopped onion and cook until softened, about 3-4 minutes. If using, add the minced garlic and cook for another 30 seconds until fragrant.

Add the halved cherry tomatoes to the pan and cook, stirring occasionally, until they start to soften and burst, about 5-7 minutes.

Stir in the cooked chicken and cream (grietinėle). Bring the sauce to a gentle simmer and cook for 2-3 minutes, allowing it to thicken slightly.

Season the sauce with salt and pepper to taste.

Drain the cooked spaghetti and add it directly to the pan with the sauce. Toss everything together until the pasta is well coated.

Serve immediately, perhaps with an optional garnish if you have one handy!