Cut pork tenderloin into 1-inch thick medallions; sprinkle with a pinch each salt and pepper.
Heat a large skillet over medium-high heat. Add butter and swirl to coat pan. Brown pork, turning once, for about 1 minute per side or until golden. Transfer to a plate.
Add garlic, prosciutto and sage to pan and sauté for about 2 minutes or until prosciutto starts to brown. Add vinegar and boil, scraping up bits stuck to pan. Stir in cream; bring to a boil, stirring. Reduce heat and simmer, stirring often, for about 5 minutes, ,until sauce is slightly thickened.
Stir in pork with any accumulated juices and tomatoes. Simmer, stirring and turning pork once, for about 5 minutes or just until a hint of pink remains in pork. Season to taste with salt and pepper. Serve sprinkled with basil and Parmesan cheese.
COOKING TIP: Choose the ripest tomatoes possible for the best flavor. Often plum (Roma) or grape tomatoes have better flavor when regular ones are out of season.