In a small bowl, stir together the cream cheese, low-fat plain Greek-style yogurt, sliced fresh chives, chopped fresh dill, and ground pepper until the mixture is smooth and evenly combined.

Lightly toast the two slices of whole-wheat sandwich bread until golden but still soft enough to bite through easily.

Spread the prepared cream cheese mixture evenly on one side of each slice of toasted bread. Then, layer the tomato slices over the spread on one slice.

Top the tomatoes with the second slice of bread, spread-side down. Carefully cut the sandwich in half diagonally and serve immediately.