Slice grape tomatoes in half and place in a large bowl. Chop red onion and mozzarella and add to bowl.
Peel cucumber. Slice in half lengthwise, use a spoon to scrape out the seeds, discard seeds. Slice in half lengthwise again, then chop cucumber into small pieces. Add to bowl.
Chop dill, set aside.
In a small bowl, mix olive oil, vinegar, lemon juice, SPLENDA, garlic powder, onion powder and fresh dill. Whisk until emulsified. Adjust to taste with salt and pepper, and additional dill if desired.
Stir dressing into the salad and mix well. Cover and refrigerate for at least three hours.
When serving, use a slotted spoon to serve as there will be additional juices at the bottom of the bowl.