Peel the onions and garlic cloves, then chop them finely.
Pour the olive oil into a large skillet and heat over high heat. Add the onions and garlic, then let them sweat for about 3 minutes until they become tender and translucent. Next, stir in the ground beef and continue cooking for 3 to 4 minutes, stirring frequently, until the meat is well browned.
Add the peeled tomatoes and the sprigs of thyme. Season with salt and pepper, stir thoroughly, then reduce the heat. Let simmer gently for about 10 minutes, stirring occasionally to bring out the flavors.
Meanwhile, bring a large pot of salted water to a boil. Add the spaghetti and cook it according to the package directions, until al dente. Drain the pasta and keep it warm.
Check the seasoning of the sauce and adjust if necessary. Divide the spaghetti among the plates, top generously with Bolognese sauce, and serve immediately.
