In a large skillet, melt butter over medium-high heat. Stir garlic into sizzling hot butter, and then arrange as many sliced pork tenderloin strips as you can fit into the pan. Cook, turning occasionally, until browned on both sides. Remove from pan; set aside. Repeat with any remaining pork tenderloin strips.
Return all pork tenderloin strips to pan. Stir in tomatoes and season with basil, salt, and pepper. Cook until mixture comes to a boil, then reduce heat to low, and cover.
Meanwhile, heat water in a nonstick skillet over medium heat. Cook peppers and onion in boiling-hot water until vegetables are tender-crisp. Stir into pork tenderloin and tomatoes. Continue cooking until pork tenderloin strips are no longer pink, about 50 to 60 minutes.