Cook the noodles al dente. In the meantime, heat the olive oil in a pan and fry the onion until translucent. Add the tuna. After 3 minutes add the tomatoes and simmer everything over medium heat.
After 6 minutes, season with salt and pepper and season with thyme. Add the capers and stew until the noodles are cooked through. Mix the pasta with the sauce and add the parsley. Serve without parmesan.