Chop the onions and garlic, and cut the turkey breast into small pieces.
Melt the butter in a pot on high heat, but don't brown it.
Sauté the onions and the garlic in the butter for about 1 minute.
Add the canned crushed tomatos, suger salt and peber to taste, and let it simmer with a lid on for 10 min.
Take off the lid, and let it simmer for another 10 minutes.
Begin to cook the penne by following the instruction on the package.
While you're cooking the penne, add the sliced turkey breast to the tomato sauce, and cook it under a lid, till the turkey is cooked through.
Cut the cherry tomatos in half.
When the turkey is cooked through, add the cherry tomatos and let it simmer for about 1 minute, and add more salt and peber if needed.
When the tomato sauce is done, add the penne and tomato sauce to a large bowl, and mix it well together.
Add the shredded mozzarella cheese, and mix it well together, untill the cheese is melted.